EP PE DEM Belg 0s Cm 1 leat
be
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ly ee:
THE
PROGrE DINGS
OF THE
Peay SOCIETY
OF
Nisa Sears “Woes
FOR THE YEAR
1958
VOL. LXXXIII.
WITH SIX PLATES. 392 Text-figures.
SYDNEY: PRINTED AND PUBLISHED FOR THE SOCIETY BY
AUSTRALASIAN MEDICAL PUBLISHING CO. LTD. Seamer Street, Glebe, Sydney,
and SOLD BY THE SOCIETY, 1959.
CONTENTS.
CONTENTS GE PROCEEDINGS, 1258
PART 1 (No. 386). (Issued 24th March, 1958.)
Pages Presidential Address, delivered at the Highty-third Annual General Meeting, 26th March, 1958, by Dr. Lilian R. Fraser: Summanryvwot Years) "Activities! 29 2) i) 5 eee ce te Os eee 1- 5 Virus Diseases of Citrus in Australia .. .. .. .. .. .. .. .. 9-19 ISTE CEIONGS! kiss. os neieiny, ROR” ul behdan Meeewe fetes, ura Test ceaien Peed deseies genclset cameras ict cis met Lali 5 Batamce Sheets for the Year ending 28th February, 1958 .. .. .. .. .. 6— 8 Seed Coat Anatomy and Taxonomy in Eucalyptus. I. By E. Gauba and L. D. Pryor. (Plate i; nineteen Text-figures. ) Rea MERI oe See ee as deo 20-32 A New Spécies of Aédes (Finlaya) from Northern Australia (Diptera, Culicidae). By Elizabeth N. Marks and Ernest P. Hodgkin. (One Text-figure.) .. .. 33-39 A Summary of the Atopomelinae (Acarina, Listrophoridae). By R. Domrow. (Nine Text-figures. ) Pe ee ae ee Me oka eS ee at es 40--54 Inheritance of Oil Characters in Hucalyptus. By L. D. Pryor and L. H. Bryant. (Five Text-figures.) Sey a, Monee crsis! made,” Mote Re gietcy (a Atel ic amiga noe ies 55-64
The Status of Nitrogen in the Hawkesbury Sandstone Soils and their Plant Communities in the Sydney District. II. The Distribution and Circulation of Nitrogen. By Nola J. Hannon, Linnean Macleay Fellow of the Society in Botany. (Two Text-figures.) Rn ERE ae a Ae ens re ein, eo 65-85
CONTENTS.
PART 2 (No. 387). (Issued 26th September, 1958.)
Pollen and Pollination in the Hupomatiaceae. By A. T. Hotchkiss. (Plate ii; twenty-six Text-figures. )
The Species of the Genus Hrodium L’Hér. endemic to Australia. (With a Key to all the Taxa known to occur in Australia.) By R. C. Carolin. (Twenty- eight Text-figures.)
Catalogue of Australian Mammals and their Recorded Internal Parasites. I-IV. By M. Josephine Mackerras. (Communicated by Dr. I. M. Mackerras.)
Studies of Nitrogen-Fixing Bacteria. VII. Cytochromes of Azotobacteriaceae. By F. J. Moss and Y. T. Tchan
Migration and Utilization of Reserve Substances during Flight in Aphis craccivora Koch. By M. Casimir. (One Text-figure.)
A New Bird-Flea from Tasmania. By F. G. A. M. Smit. (Communicated by Mr. D. J. Lee.) (Ten Text-figures.)
Widespread Natural Infection of Barberry by Puccinia graminis in Tasmania. By I. A. Watson and N. H. Luig
Systematic Notes on Some Eastern Australian Members of the Papilionaceae. By Joy Thompson
Somatic Hybridization in Puccinia graminis var. tritici. By I. A. Watson and N. H. Luig
A Note on the Status of Aphodius tasmaniae Hope. By B. B. Given. (Com- municated by Mr. C. E. Chadwick.)
Sir William Macleay Memorial Lecture. Timing in Human Evolution. By A. A. Abbie. (Seven Text-figures. )
Some More Bark- and Timber-Beetles from Australia. 158. Contribution to the Morphology and Taxonomy of the Scolytoidea. By Karl E. Schedl. (Com- municated by Dr. A. J. Nicholson.)
Two New Species of Hemicycliophora (Nematoda : Tylenchida). By M. R. Sauer. (Communicated by Mr. A. J. Bearup.) (Two Text-figures.)
A New Species of Frog of the Genus OCrinia Tschudi from South-Hastern Australia. By Murray J. Littlejohn. (Communicated by Mr. S. J. Copland.)
92-100
.. 101-160
.. 161-164
. 165-172
.. 173-180
. 181-186
. 187-189
. 190-195
196
.. 197-213
. 214-216
. 217-221
222-226
(7389
CONTENTS.
PART 3 (No. 388). (Issued 23rd March, 1959.)
Acarina from Australian Bats. By Robert Domrow. (Twenty-six Text-figures.)
A Turbidimetrie Method for Estimating the Number of Nematode Larvae in a Suspension. By C. D. Blake. (Two Text-figures.) The Oviposition Behaviour of Aédes australis (Erickson) (Diptera, Culicidae). By A. K. O’Gower. .. Palaeozoic Geology of the Cooleman Caves District, New South Wales. By N. C. Stevens. (Plates iii-iv; one Text-figure.)
Melampsora lini (Pers.) Lév. Uredospore Longevity and Germination, By H. B. Kerr. (Three text-figures.) On some Pergine Sawflies reared by Mr. M. F. Leask (Hymenoptera, Pergidae). By Robert B. Benson. (Communicated by Mr. K. EH. W. Salter.) (One Text-figure. ) The Diptera of Katoomba. Part 2. Leptidae and Dolichopodidae. By G. H. Hardy. (Nine Text-figures.)
Bat-infesting Ornithodoros (Ixodoidea-Argasidae) of the Oriental-Australian Region. By L. J. Dumbleton. (Communicated by Dr. J. W. Evans.)
(Highteen Text-figures. )
Notes on Australian Thynninae. II. The Genera Dimorphothynnus, Rhagigaster and Hirone. By B. B. Given. (Communicated by Dr. A. J. Nicholson.) (One hundred and twenty-six Text-figures.)
Notes on Australian Thynninae. III. The Genus Thynnoides. By B. B. Given. (Communicated by Dr. A. J. Nicholson.) (Wighty-eight Text-figures. )
Australasian Ceratopogonidae (Diptera, Nematocera). Part VIII. A New Genus from Western Australia attacking Man. By Willis W. Wirth and David J. Lee. (Five Text-figures. )
Mode of Inheritance of Resistance to Powdery Mildew in Barley and Evidence
for an Allelic Series Conditioning Reaction. By N. H. Luig, K. S. McWhirter and EH. P. Baker.
Spores and Pollens from a Permian-Triassic Transition, N.S.W. By J. P. F. Hennelly. (Plates v-vi; two Text-figures.)
Abstract of Proceedings
List of Members
List of Plates
List of New Genera, Species, Subspecies and Name ..
Index
Pages 227-240
. 241-244
. 245-250
. 251-258
. 259-287
.. 288-290
.. 291-302
. 303-308
.. 309-326
. 327-336
.. 337-339
.. 340-362
. 363-369 . 371-376 . 377-882
383 383
- 384-387
ANNUAL GENERAL MEETING. 26th Mancu, 1958.
The Highty-Third Annual General Meeting was held in the Society’s Rooms, Science House, 157 Gloucester Street, Sydney, on Wednesday, 26th March, 1958.
Dr. Lilian R. Fraser, President, occupied the chair. é
The minutes of the Highty-Second Annual General Meeting, 27th March, 1957, were read and confirmed.
PRESIDENTIAL ADDRESS.
It is first my pleasant duty to convey to the Society’s honorary officers, Dr. W. R. Browne and Dr. A. B. Walkom, our deep appreciation of their work during the past year. It is impossible to overemphasize the debt which we owe to these gentlemen for their services in an honorary capacity, as secretary, treasurer and editor, their invaluable experience in all branches of the Society’s functions and organization, and their patience and good humour in dealing with the occasional problems which arise. I must also express our appreciation of the services of the assistant secretary, Miss Allpress, who watches over the needs of secretary and treasurer, Council members and ordinary members alike, and ensures the smooth running of day-to-day activities. I should also like to record my personal indebtedness to the Council for their support during the past year.
Parts 1 and 2 of Volume 82 of the Society’s PROCEEDINGS were published in 1957, and Part 3 in March, 1958. Volume 82 consists of 384 pages, 14 plates and 190 text-figures. A contribution of £50 towards the cost of publication of “Australian Tree Frogs of the Genus Hyla’* was made by Mr. S. J. Copland. A leaflet, giving a short account of the history, aims and objects of the Society has been issued for prospective members and others who may be interested in the Society’s activities; forms for application for admission as an Associate are also now available.
During the year 21 new members were added to the list, two members died, three resigned and two were removed from the list under Rule VII. The numerical strength of the Society at 28th February, 1958, was: Ordinary Members, 225; Life Members, 32; Corresponding Members, 2; Associate Member, 1; total 260.
Members will note that during the year fluorescent lighting was installed in the meeting room and the ceiling and walls were painted. It was decided by Council that ordinary monthly meetings during 1958 should commence at 6 p.m., instead of 7.30 p.m. This experiment was started during 1957 in the hope that members might find the earlier meeting time more convenient than the latter. The changed time appears to have resulted in rather larger attendances at most meetings.
Council resolved to establish a Sir William Macleay Memorial Lecture to be given biennially in some branch of science covered by the Society’s activities, the text of the lecture to be published in the Procrrpines. The first lecture has been fixed for Thursday, 19th June, 1958, Professor A. A. Abbie, of Adelaide, having consented to deliver it.
Lecturettes were given at the following monthly meetings: April: New Caledonia and its Plants, by Dr. H. S. McKee; May: A Visit to Some American Universities and Marine Biological Stations, by Miss Isobel I. Bennett; June: Some Aspects of Plant Distribution in Southern Africa, by Dr. A. R. H. Martin; July: Some Aspects of the Biology of the Bandicoot, by Mr. Gordon Lyne; October: Social Behaviour in the Australian Bulldog Ants, by Mr. John Freeland. On 25th September, 1957, commemoration was made of the 250th anniversary of the birth of Linnaeus. An article on the botanical work of Linnaeus, written by Mr. L. A. S. Johnson, was,
PROCEEDINGS OF THE LINNEAN Society or NEw SoutH WALES, 1958, Vol. Ixxxiii, Part 1.
A
2 ANNUAL GENERAL MEETING.
in his unavoidable absence, read by Miss Mary D. Tindale, and Mr. G. P. Whitley gave an illustrated talk on the life and zoological work of Linnaeus, exhibiting first editions and other interesting “Linnaeana’”’. We wish to express our appreciation and thanks to all lecturers for their interesting contributions to our meetings. Members again showed keen interest in bringing notes and exhibits.
Library accessions from scientific societies and institutions were slightly fewer than in previous years, the total being 1,858. Requests for library loans and the demand for reprints continued to be made as frequently as previously. Mrs. F. C. Blanchard, a daughter of Dr. N. A. Cobb who was a member of the Society from 1889. to 1906, forwarded a reprint for the Society’s library of ‘Nathan A. Cobb, Botanist. and Zoologist, a Pioneer Scientist in Australia’ (from “the Asa Gray Bulletin’, n. s. Vol. 3, No. 2, pp. 205-272, 1957). A first edition of ‘“Lachesis Lapponica, or a Tour in Lapland, now first published from the original manuscript journal of the celebrated Linnaeus” (2 vols. in one), by J. EH. Smith, London, 1811, was presented to the Society on the occasion of its celebration of the 250th anniversary of the birth of. Linnaeus, by Mr. A. EH. Jobson. Mr. David S. Macmillan presented to the Society a copy of his book “A Squatter Went to Sea. The Story of Sir William Macleay’s New Guinea Expedition (1875) and his Life in Sydney”, in which due acknowledgement was made of his use of extracts from Sir William Macleay’s diary and other sources. on the “Chevert” expedition in the possession of the Society. In January, the library was thoroughly cleaned and dusted. During the year steel shelving was installed in the storeroom to accommodate the stock of PRocEEDINGS, which has been rearranged and checked. ;
Council has decided that in future the price of the Macleay Memorial Volume shall be £1. 1s., post free, instead of £2. 2s. as previously.
The Society, through its Council, has supported the efforts made to oppose the renewal of grazing leases in the Snowy Mountains area in the interests of soil conserva- tion and prevention of soil erosion. The Society was represented at conferences held. during the year of bodies interested in conservation. A report supporting the reservation. of the Deep Creek area was forwarded to the Cumberland County Council. The Society has also taken up Corporate Membership of the National Parks Association of New South Wales, Central Region. Following the receipt of representations from the Joint Scientific Advisory Committee the Council adopted two resolutions regarding the Kosciusko area, the first strongly deprecating any proposal that there should be a return to snow-lease grazing and the second urging the Kosciusko State Park Trust. to take immediate action in regard to the setting apart of a Primitive Area. The resolutions were forwarded to appropriate State Ministers and to the Kosciusko State Park Trust respectively.
The total net return from the Society’s one-third ownership of Science House: for the year was £1,065. The rental determinations of the Fair Rents Board as from. ist October, 1957, gave an increase of 19% to the rents in Science House, the Society’s. rent of rooms and storeroom being now £813 as against the previous approximate amount of £648.
It is my pleasure to offer congratulations to Dr. Germaine A. Joplin on the award of a Carnegie Grant for study in the United States of America, and to Professor J. M. Vincent on the award of the medal of the Australian Institute of Agricultural Science.
Linnean Macleay Fellowships. :
In November, 1956, the Council reappointed Miss Nola J. Hannon and Mrs. Mary B.. Williams to Fellowships in Botany for 1957.
During the earlier months of 1957 Miss Hannon devoted her time to the compilation of unrecorded observations and unpublished files of relevance to the status of nitrogen in the Hawkesbury Sandstone ecosystems. This information covered a wide variety of subject matter and was obtained from private firms and individuals and government officials. By combining these data with those that had been collected during the three-year tenure of the Linnean Macleay Fellowship, a general survey of nitrogen in these communities was completed. A second paper in the series “The Status of
ANNUAL GENERAL MEETING. 3
Nitrogen in the Hawkesbury Sandstone Soils and their Plant Communities in the Sydney District. The Distribution and Circulation of Nitrogen” has been accepted for publication in the Procrepines and further papers are being prepared. Investiga- tions of the native rhizobial population have been concerned with the effectiveness of the symbiotic associations with Acacia suaveolens (Sm.) Willd., the cultural charac- teristics and the nutritional requirements of isolates chiefly from the Sydney sandstone soils.
During 1957, Mrs. Williams continued her study of the family of freshwater Algae, the Characeae. More determinations of chromosome numbers were made. A provisional count of 18 chromosomes was made on Nitella stuartii A. Br., the one member so far collected of the section Anarthrodactylae. It was particularly interesting to find that a member of this section had a chromosome number conforming to the basic number, nine, as determined for other sections of the genus, although the uniformity of numbers does not give any clues to possible phylogenetic relationships within the genus. Within certain species, however, it has been established that the chromosome number may vary according to locality, so that several “chromosome races” have been found, forming polyploid series within these species. Further investigations were made into the dormancy of Chara australis spores; treatments included pretreatment at 5°C. for 140 days, pretreatment with cold concentrated sulphuric acid, and pretreatment with infusions of rotting Chara plants. A low percentage germination was obtained in some cases, but no method gave 100% breaking of dormancy. It seems likely that dormancy in Chara spores is a complex phenomenon, which is not overcome by single treatments.
In November, 1957, the Council reappointed Miss Nola Hannon and Mrs. Mary Williams to Fellowships in Botany for 1958.
In consequence of her appointment to a lectureship in the N.S.W. University of Technology the resignation of Miss Hannon from her Fellowship as from 11th April, 1958, has been accepted by Council. We congratulate her on her new appointment. It is hoped that Parts III-VI of ‘The Status of Nitrogen in the Hawkesbury Sandstone Soils and their Plant Communities in the Sydney District’, together with two other papers, will be submitted shortly for publication in the PROCEEDINGS.
During 1958, Mrs. Williams, who will be working in the Department of Botany, University of New England, instead of the University of Sydney, proposes to continue her work on the Australian Characeae. Owing to the recent disastrous fire in the Department of Botany, University of New England, in which Mrs. Williams lost much material, her work has necessitated replanning, which is not yet complete. We wish her every success in her research work.
Linnean Macleay Lectureship in Microbiology.
Dr. Y. T. Tchan, who was appointed Linnean Macleay Lecturer in Microbiology as from ist August, 1955, has furnished reports from the date of his appointment to 3lst December, 1957. His activities may be summarized as: (1) Teaching: His first year was mainly used for organizing lectures and practical classes. Complete new courses dealing with microscopy, infectious bacteria and bacterial and protozoan systematics were prepared for Science and Agriculture students. These courses were then modified in the second year in the light of the previous year’s experience. (2) Research: Some of the research has been carried out with financial assistance from C.S.I.R.O. (Land Survey and Utilization Section). The survey of the distribution of Beijerinckia in Northern Australia was continued and some physiological studies of representatives of the genus were made. Studies of Northern Territory soils (Katherine Station soils) were made. A complete bacteriological analysis of these soils was completed. (3) Microscopy: In conjunction with the University Hxtension Board, a post-graduate course on Light Microscopy was given. The lectures have been attended by research workers of various biological disciplines. Also, in collaboration with Dr. W. H. Steel, of C.S.I.R.O., a paper is in preparation for publication on the theoretical implications of overlap in phase microscope image formation. (4) N-fization. bacteria: In collaboration with Dr. F. Moss, Department of Bacteriology, Sydney
4 ANNUAL GENERAL MEETING.
University, a paper is under preparation on the subject of cytochromes of Azoto- bacteriaceae. (5) Fertility test: Using the algal method the P availability could be determined. Good correlations have been obtained with higher plants. (Part of this programme was carried out with the collaboration of Mr. R. Hawkes.) (6) A new project on the Northern Territory soils has been started. It is aimed to study the N fixation algal population and its ecological conditions.
In the year 1956-57, more work on the soil algae was done. A new approach to the soil fertility test with algae was made. Some very promising results were obtained for nitrogen estimation by this means. The technique also seems applicable for phosphorus estimation. Further work is needed before any conclusion can be reached. A preliminary paper has been published (VI Congres internationale de la Science du sol, 1956). An improved technique of fluorescence-phase microscopy has been developed and a short paper has been accepted for publication in Nature. A new species of Beijerinckia has been described in a paper published in Part 3 of the Society’s PROCEEDINGS.
In connection with the Bacteriology Fund, it is reported that the property at 53 Margate Street, Ramsgate. N.S.W., has been sold for £4,250, £2,200 of which remains under a 15-years’ mortgage bearing interest at 7% per annum, the mortgagors having the right to repay the whole of the principal on three months’ notice and the additional right of reducing the principal sum by £50 per annum or multiples of £50.
Obituaries.
It is recorded with regret that the following members died during the year:
Emeritus Professor Wiitt1Am Nort Benson, B.A., D.Sc., F.R.S., F.G.S., who had been a member of the Society since 1907, died at Dunedin, New Zealand, on 20th August, 1957. He was born near London on 26th December, 1885, and educated at the Friends’ High School in Hobart and later at the University of Tasmania and the University of Sydney, where he came under the influence of the inspiring personality and teaching of Sir Edgeworth David. From 1914 to 1916 he held a Linnean Macleay Fellowship in Geology. He contributed ten papers to the Society’s PROCEEDINGS; also one with F. Chapman and one with W. S. Dun and W. R. Browne. These papers included his classic study of the geology and petrology of the Great Serpentine Belt of New South Wales He was Professor of Geology at the University of Otago, Dunedin, from 1917 to 1949. In Dunedin he turned his attention io problems of New Zealand geology as well as its relation to the south-west Pacific as a whole.
During his life-tinie Professor Benson received many honours. He was a foundation Fellow of the Australian and New Zealand Assosciation for the Advancement of Science, and its Mueller Medallist (1951); Fellow of the New Zealand Institute, later Royal Society of New Zealand (1926); Hector medallist (1933), Hutton medallist (1944) and president (1945-47) of the same Society; Lyell medallist of the Geological Society of London (1939); Fellow of the Royal Society (1941); Clarke medallist of the Royal Society of New South Wales (1945); correspondent of the Geological Society of America (1949); honorary D.Sc., University of New Zealand (1951), and honorary member of the Mineralogical Society (1954).
Mr. Davin Grorcr STEAD died at Watson’s Bay, Sydney, on 2nd August, 1957. He had been a member of the Society since 1898, thus being the oldest member at the time of his death. He was a noted authority on fishes and an all-round naturalist. For many years he was actively interested in the work of the Wild Life Preservation Society and the Royal Zoological Society of New South Wales. He contributed two papers (1898 and 1899) to the Society’s ProcrEEpINGsS and in his earlier years took a keen interest in the Society's meetings and made presentations of books to the Society’s library.
PRESIDENTIAL ADDRESS. Virus Diseases of Citrus Trees in Australia. Seven diseases caused by virus infection are known to affect citrus trees in Australia. Two of these, scalybutt of Poncirus trifoliata rootstock, and stem pitting disease of grapefruit, are of major importance; tristeza, a very important disease
ANNUAL GENERAL MEETING. 5
elsewhere, is not a problem in Australia, and psorosis, crinkly leaf, woody gall and enation are minor or unimportant. The major symptoms, distribution, importance and method of control are discussed. Brief reference is made to two virus diseases, stubborn and xyloporosis, which are important overseas but not as yet definitely known to be present in Australia. (For full text, see pp. 9-19.)
The Honorary Treasurer, Dr. A. B. Walkom, presented the balance sheets for the year ended 28th February, 1958, duly signed by the Auditor, Mr. S. J. Rayment, F.C.A. (Aust.), and his motion that they be received and adopted was carried unanimously.
No nominations of other candidates having been received, the Chairman declared. the following elections for the ensuing year to be duly made: President: S. Smith-White, D.Sc.Agr. Members of Council: A. J. Bearup, B.Sc.; F. V. Mercer, B.Sc., Ph.D.; S. Smith- White, D.Sc.Agr.; EH. Le G. Troughton, C.M.Z.S., F.R.Z.S.; H. S. H. Wardlaw, D.Se., F.R.A.C.I.; and A. R. Woodhill, D.Sc.Agr. Auditor: S. J. Rayment, F.C.A. (Aust.).
A cordial vote of thanks to the retiring President was carried by acclamation.
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PRESIDENTIAL ADDRESS.
VIRUS DISEASES OF CITRUS IN AUSTRALIA. By LiniaAn R. FRASER.
(Detivered 26th March, 1958.)
Studies of plant viruses are of two general types, those which seek to elucidate the disease condition caused by a virus, its vector relationships, variation in host reaction, influence of environment, virus strain relationships, etc., and those which seek to investigate the virus itself as an entity by biochemical or biophysical means. These fundamental studies are providing the foundations upon which some rational system of virus taxonemy may in the future be based, and have already made it possible to demonstrate or ecorfirm relationship or lack cf relationship in certain virus groups. This type of study is so far only possible with easily handled, stable and highly infectious viruses, and the diseases of woody perennial plants, for the most part, do not come into this category. ‘The study of the citrus viruses is still largely in the stage of disease delineation, and the identification of a virus is based on the symptoms produced in inoculated seediings, and relationships are assumed on the basis of general similarity of symptoms. The need for precise means of establishing relationships is urgent.
There are a number of special disease problems of perennial vegetatively propagated plants which are particularly important in citrus. The first is the accumulation of virus diseases and their propagation and spread in vegetative plant parts. Varieties of orange or grapefruit or mandarin, locally esteemed, are imported into other countries, taking with them any virus which they may be carrying. The second is the existence of symptomless carriers which makes the accumulation of viruses so dangerous. Varieties and species of citrus vary very greatly in their reaction to infection by a particular virus. In some cases an apparently quite healthy plant can carry a virus which is damaging or lethal to other varieties or combinations of varieties. A third problem is that of latency. Some viruses may take many years to preduce recognizable symptoms even on susceptible varieties, and during the period of latency such affected plants can be used as a source of propagation material in ignorance, with conseauent spread of the disease.
The complete examination of a new virus proklem involves not only a study of behaviour in the field, but a search for indicaters, i.e. varieties which, when inoculated, will give ar unmistakable, specific and reasonably rapid reaction. Only when such indicators are available is it possible to make surveys of suspect populations, to index material for disease freedom sc that sources of disease-free material for propagation can be built up and to screen introductions from foreign countries. Confusion can occur if more than one virus is present, and the search for indicators which will adequately separate different viruses has been beset by pitfalls arising from this cause. The danger here is that if more than one virus is present the reactions which develop on indicators may be attributed to one cause only rather than several.
The identification of disease relationships has been based largely on symptom comparison. Attempts have been made to apply the technique of cross protection, but this without corroborative evidence is not entirely reliable. Symptom expression even in a single strain can vary under differing environmental conditions and almost every virus appears to exist in numbers of strains. In addition there is convergence of symptom type by apparently distinct viruses. These points make it clear that
PROCEEDINGS OF THE LINNEAN Society oF NEw SoutTH WALES, 1958, Vol. Ixxiii, Part. 1.
10 VIRUS DISEASES OF CITRUS IN AUSTRALIA,
considerable caution must be exercised in the identification of viruses and that much more exact information is required on all the diseases which are here discussed and the range of variation which can occur. Technical difficulties also are associated with the study of virus diseases of trees, which make progress in this field somewhat slow. All citrus viruses so far known must be transferred by budding, grafting, or by means of insects. No meehanical means of inoculation is available. All are restricted to citrus, and citrus seedlings must be used as indicators.
Some of the diseases can take years to produce symptoms, necessitating considerable space for trials, and making such investigations costly and time-consuming. The process of testing and selecting varieties suitable for survey and indexing is slow, and ensuring that the symptoms produced are of the virus under study, and are not modified by the presence of other, perhaps latent, viruses, is also slow and sometimes difficult.
Citrus in Australia: Native Species. 2
No species of the genus Citrus is native to Australia, but the closely related genera of the Citrinae, Hremocitrus and Microcitrus, are represented by one and five species respectively. The Australian desert lime Hremocitrus glauca is a shrubby species native to arid western New South Wales and south-western Queensland, and Microcitrus australis, M. australasica, M. inodora, M. maidenii and M. garrowayi occur, though not commonly, in eastern Queensiand rainforest areas, the first two extending into northern New South Wales. There is no evidence to suggest that any of the virus conditions affecting citrus in Australia are endemic to this country. Three collections of Hremocitrus glauca have been made from localities in western New South Wales and seven of WMicrocitrus australasica from north-eastern New South Wales and southern Queensland. All of these proved to be free of detectable virus infection.
Introduction of Citrus.
The introduction of citrus to Australia commenced with the first settlement of the colony in New South Wales. Seeds and plants of a number of varieties were brought by the first fleet and planted at Port Jackson in 1788 (Bowman, 1956), and in subsequent years new and desirable varieties were introduced from all citrus-growing countries. At first trees were usually grown from seed or layers but it was soon found that trees budded on selected stocks were superior. By 1835 nurseries round Sydney were producing thousands of such trees and the industry was flourishing. There was at first no restriction on imports of plants and no examination for presence of disease or pests, but since 1908 quarantine restrictions have slowed up the volume of introductions and perhaps saved us from some troubles present commonly in other lands.
Virus Diseases Known to Occur in New South Wales.
I will refer briefly to seven diseases shown to be virus in cause, which have been found to be present in Australia. A number of other diseases, quite serious in their effect, are almost certainly of virus origin but proof has not yet been obtained; these will not be included. Finally, I shall very briefly refer to two virus diseases of importance overseas which are not yet definitely known to be present here.
Psorosis.
This virus is bud transmissible and no insect vector is known. It is of very minor importance in most citrus growing areas of Australia but is a major cause of tree decline in the U.S.A. and Mediterranean countries and appears also to be common in the Orient. The symptoms are scaling or exfoliation of bark in patches on limbs and trunk, which does not begin to develop until the trees are eight to twenty years old or older, and is associated with slow deterioration and death. A virus pattern of flecks or oak-leaf markings occurs on immature ‘foliage in the spring and sometimes in the autumn, and the disease can be diagnosed in affected trees by means of this symptom before the scaling starts, and suspect trees can be indexed onto young seedlings of orange and mandarin for the production of this symptom.
We have no record of the first entry of this disease into Australia, but locally propagated trees now 45 and 50 years old are known to carry it.
BY LILIAN R. FRASER. 11
The common type of psorosis appears to be identical with that described as psorosis A in California (Fawcett and Bitancourt, 1943) but the range of symptom development is extreme. In some orchards some affected trees start to produce ‘Sealing at 12 years and almost all trees show this symptom by the age of 20 years. A number of orchards are known where scaling was observed for the first time in a few trees at the age of 25 or 26 years, but the great majority are still vigorous and productive at 48 to 50 years, though the presence of leaf patterns in the spring proves that they also are infected. At least one orchard is known where the trees are more than 40 years of age and no bark symptoms have occurred in any of them, though leaf patterns are produced. One case has been investigated of trees known to have been propagated from a single bud source. Of 63 trees 35 years old only three have well-developed bark symptoms but all show strong leaf pattern development ‘and are not otherwise affected. The reason for this variability is not known, but the simplest explanation is that the virus exists as a number of strains of differing virulence.
The relative unimportance of psorosis in Australia can be attributed in part to the fortunate chance that few infected trees were imported in the early years of eitrus growing, in part to the restrictions which in recent years have limited the free importation of budwood, and in part to the activity of a bud-selection society in New South Wales which was controlled by the nursery industry with assistance from the Department of Agriculture and operated from 1935. Though certification was largely on agronomic characters, the parent trees chosen had to be mature and of ~ good habit and no budwood was cut from trees showing symptoms of disease. Since 1953 a more rigid bud registration scheme has been in operation which guarantees freedom from this disease. In Queensland since 1934 budwood from disease-free ‘sources has been provided for nurserymen by the Queensland Department of Agriculture.
No citrus species or varieties are known which are not susceptible to infection, but lemons, Seville oranges, rough lemon and possibly others can carry the virus without production of bark symptoms.
The original home of psorosis is not known, but may have been in Asia, where it is believed to be common.
Lemon Crinkly Leaf.
This virus is bud transmissible and no vector is known. It affects lemons, producing crinkled foliage and protuberances on the fruit rind. Sometimes the whole tree may be affected but more often symptoms are restricted to a few or only one limb. There is evidence of the existence of strains of differing severity (Fraser, unpublished). Trees affected by a severe strain have a somewhat upright habit and reduced vigour, other strains have a negligible effect on vigour and productiveness. It has a somewhat restricted distribution in New South Wales and Victoria, and has been recorded in Western Australia on trees imported from New South Wales. It was described originally from California (Fawcett, 1936; Fawcett and Bitancourt, 1943), and was included in the psorosis group. No information is available relating ‘to its presence in other countries.
Seedlings of Hureka lemon are useful as indicators for crinkly leaf if no other virus is present. ‘Six weeks after inoculation small star-like spots occur in immature leaves, followed by crinkled growth as the leaf enlarges and matures. Sweet orange, Mandarin and rough lemon seedlings inoculated with crinkly leaf develop a few star-like spots in the young foliage and occasionally one or two crinkled areas, but for all practical purposes are symptomless.
Enation.
This virus is transmitted by budding, and very readily by the tropical citrus aphid Toxoptera citricidus and probably by other aphids also. It was described originally from California (Wallace and Drake, 1953) and later from South Africa (McClean, 1954) where it was found during surveys for tristeza virus. In Australia -also its presence was detected during surveys for other diseases (Fraser, unpublished). Small enations, or outgrowths on lower surfaces of the main veins, are produced on
12 VIRUS DISEASES OF CITRUS IN AUSTRALIA,
seedling rough lemon and, if no other virus is present, on grapefruit, Seville orange: and acid limes. In sweet orange and mandarin there is no reaction, or at most a very weak slight development on very young rapidly growing seedlings. It appears to be widespread in New South Wales but of no discernible importance. It is likely that strains of different virulence occur since some isolates produce many large enations. on rough lemon seedlings and others few and small.
Woody Gall.
This condition has been under observation in New South Wales for some years: and has been shown to be due to a bud transmissible virus (Fraser, unpublished). Its: prevalence in several naturalized seedling communities of rough lemon suggested that. it has an active vector. The symptoms are woody galls on branches older than one season and on the main trunk and on the upper roots. These are smooth, covered with normal bark and may be single rounded swellings or large-knobbed or cauliflower-- like structures. It is possible that strains of differing virulence occur since some: affected trees have only a few minor swellings and in others the swellings become large. Orange and mandarin trees on affected stocks show no gall development even when substantial outgrowths are present on the stock below the bud union. No significant reduction in vigour of the scion is associated with infection of rootstocks,, but affected rough lemon seedling trees are lacking in vigour. It is common in many, localities. Rough lemon seedlings have been used as indicators.
Scaly Butt of Poncirus trifoliata (Hxocortis).
This virus is bud transmissible and no insect vector is known (Benton e#¢ al., 1950,. 1952). It is carried symptomlessly in orange, mandarin, grapefruit and rough lemon, but in Poncirus trifoliata and some of its hybrids the virus produces a bark-scaling condition which is latent for two to eight years following inoculation. Infected trees on susceptible rootstocks are considerably stunted. The spread of the disease is by means of infected budwood. No citrus varieties have so far been found which can be used in the seedling stage as indicators for demonstrating the presence of this. virus. Consequently P. trifoliata itself or one of its hybrids must be used. P. trifoliata is completely resistant to root rot caused by the fungus Phytophthora citrophthora and since 1942 has been in considerable demand in New South Wales as a stock for oranges, mandarins and grapefruit for use in areas where root rot is liable to occur. The: presence of scaly butt virus carried symptomlessly in some scion clones therefore: becomes of considerable importance.
Control of the disease has been effected by a bud registration scheme, guaranteeing” freedom from virus. Since the scaly butt virus is symptomless in trees on stocks other than P. trifoliata only trees on this stock are registered, and these must be older than ten years, so that it is certain that the virus is not present.
From field observations it appears that several strains of scaly butt occur, differing in severity and type of scaling, time of onset, and the degree of stunting which is produced in the scion tree. In addition there is a type of stunting of trees on P. trifoliata with which no scaling is associated and it is eseHme that this also may be due to a strain cf the scaly butt virus.
In New South Wales the virus appears to be universal in Hureka lemons and rather common in Washington and Thompson navel oranges, less so in Valencia oranges and grapefruit, and very unusual in mandarins. It occurs in North (Fawcett and Klotz, 1948) and South America (Knorr et al., 1951), but no information regarding its possible presence in the Orient is available. Its time of introduction cannot be stated and very little information can be obtained from current plantings, since prior to 1940 the susceptible P. trifoliata stock was of very minor importance. However, a few infected trees of Valencia and Washington navel orange propagated locally are known, which are more than 50 years of age. <A similar disease of Rangpur limes. which has been attributed to the same virus has heen described in South (Rosetti,. 1955; Moreira, 1955) and North America (Olsen and Shull, 1956; Reitz and Knorr,. 1957).
BY LILIAN R. FRASER. 13
Tristeza.
Tristeza is a virus disease which has its most serious effect on orange and mandarin trees on Seville orange stock. Trees may wilt and die in a few months after inoculation or may linger on for a number of years making very poor growth before they finally die. Its principal vector is the tropical citrus aphid, Toxoptera citricidus, but a number of other aphids can also transmit it with a rather low degree of efficiency.
The disease affects chiefly orange and mandarin varieties on Seville rootstocks. On their own roots, on rough lemon, P. trifoliata and a number of others, no symptoms are produced—the varieties are symptomless carriers. A number of other varieties used as rootstocks, including grapefruit, induce a tristeza effect in an affected scion, but combinations such as grapefruit on Seville orange or lemon on Seville orange do not decline to the same extent or in the same way, and seedling unbudded Seville oranges do not suffer. Various theories have been put forward to explain this, but none are entirely acceptable, or account for all the anomalies seen. The history of the investigation which led to the recognition of this disease has been well reviewed by Webber (1943), Wallace (1956), and Bennett and Costa (1949). It is presumed that it is endemic in oriental countries, to which the tropical citrus aphid is also endemic, but ne surveys have yet been made in India or China which might throw light on its place of origin. The recognition of the virus condition is dependent on the use of the susceptible stock and there seems to be no evidence that Seville orange is or has ever been in use as a stock in the Orient.
Seville orange came into prominence as a stock first in Spain during the middle of last century, when it was found to be very resistant to the fungus root rot caused by species of Phytophthora (Fraser, 1949). It was widely used in Mediterranean regions, where it is at present the major rootstock, and in South America and California.
Wherever its place of origin may have been, it is clear that tristeza virus and its vector must have become established in South Africa at an early stage (McClean, 1956; Webber, 1943).
One of the greatest epiphytotics of recent times occurred following the introduction of the virus into Argentina about 1930. In the following decades 7,000,000 trees of the susceptible sweet orange on Seville orange stock were destroyed in Argentina and an equal number in Brazil (Costa, 1956). In California an outbreak which is still continuing commenced in 19398 (Wallace, 1956).
Tristeza has been present in Australia, though unrecognized, for very many years, possibly from the time of the first establishment of this erop. Seeds and plants of citrus were obtained during the voyage of the first flest, from Rio de Janeiro, but tristeza virus was not present in South America at that time. The ships also touched at the Cape of Good Hope on this voyage, and though there is no specific reference it is quite possible that further citrus trees or fruit would have been obtained from the garden of the Hast India Company there. If introductions were not made then, certainly they would have occurred during later voyages. Suttor in 1843 (quoted by Bowman, 1956) mentioned having worked with success China orange to Seville orange stock, though these may have been seedling trees and therefore virus-free, and Shepherd in 1851 mentioned the production of Seville orange as a stock in the nursery.
By 1870 heavy losses of citrus trees round Sydney had been sustained from root rot. The resistance to root rot of Seville orange stock was known and its use advocated to overcome the disease, and it is clear that if it had proved generally successful it would have been widely used, but this was not so (Fraser, 1949). Alderton (1884) mentions that Seville orange, though admittedly a hardy tree, was not favoured as a rootstock because of the poor growth of trees worked onto it, and Mackay (1875), though advocating the use of Seville orange on theoretical grounds, pointed out that growers were not unanimous on the subject of the best stock. The general lack of enthusiasm for this stock can be taken to indicate its unsatisfactory behaviour even at that time, since in the absence of tristeza, Seville orange is an
14 VIRUS DISEASES OF CITRUS IN AUSTRALIA,
extremely vigorous and desirable stock. In 1890, giving evidence at an enquiry into the citrus industry, Pye, a leading grower in the Parramatta district (mear Sydney), specifically states that Seville orange stock should never be used as it had proved a complete failure. Pye also made the first reference to the vector, the citrus aphid, as being a common pest at that time. The introduction of a virus of this type into a plant community cannot have its most devastating effect unless the vector is also: present.
It seems reasonable to assume, therefore, that both the virus and its vector had been introduced at an early stage and infection had spread through the citrus population, undetected because trees were often on their own roots, seedlings or layers. When working onto rootstocks became the practice, the general preference for rough lemon stock is noted by all early writers.
There have been citrus nurseries round Sydney since the early days of citrus: culture, and when new areas were opened up in other parts of Australia, trees from these nurseries were in demand. Hence the virus was spread, unwittingly in symptomless carrier trees, to new settlements in Queensland, Western Australia and New Zealand. It is generally accepted that the epiphytotic which worked its way through South America was started by the introduction in 1930 of infected trees. on rough lemon stock from South Africa (Wallace et al., 1956). At this time also several large shipments of orange trees were sent from Sydney to growers in Argentina (Eyles, private communication) and these would undoubtedly have carried tristeza, so that Australian trees may well have contributed to the South American disaster. As McClean (1939) has emphasized, the introduction of the vector is as important as that of the virus. This also could have come from New South Wales.
In the years following 1890 a very considerable expansion of citrus growing took place in the very isolated district of Mildura on the lower Murray River, with the introduction for the first time in Australia of irrigation for fruit production in an arid area. The Chaffey Bros., irrigation engineers from California, who started this. venture, introduced budwood of favoured citrus varieties from California and also seed for stocks, the most favoured being the Seville orange, a variety now known as bitter sweet, and the bitter rough being also used. These were propagated locally and Seville orange stock was found to be extremely satisfactory and a number of excellent orchards were established. Its resistance to the fungus Phytophthora citrophthora enabled these trees to flourish where trees on rough lemon or sweet. orange gradually deteriorated with root rot. Further propagations were made and the stock enjoyed considerable local popularity. However, by 1942 some of the trees were starting to decline and now no satisfactory orchards on this stock exist. This. decline has been attributed to the introduction of tristeza virus in the Robertson navel from California (McAlpine ef al., 1948). This, however, is unlikely. A tree of Robertson navel propagated from the originally introduced budwood was located at Curlwaa in south-western New South Wales in 1948 and this proved to be free of tristeza. However, in addition to locally propagated trees, many young trees on rough lemon or sweet orange stock were brought into the lower Murray district from Sydney nurseries in the early days of the settlement and these would certainly have carried the virus. The later spread of infection to trees on Seville orange stock most probably was the result of increased activity of aphids.
This behaviour of Seville orange as a stock completely satisfactory in one district and as complete a failure in others was a challenge and a mystery to horticulturalists until the virus nature of the disease was established.
Although a very great deal of information has been obtained about tristeza, the full story of its relationships has not yet been told. Further comments on tristeza virus distribution and reaction and seedling indicators follow the discussion of stem pitting.
Stem Pitting of Grapefruit.
This disease is readily transmitted by budding and Toxoptera citricidus is an efficient vector. It was described first in South Africa (Oberholzer, 1949) and later
BY LILIAN R FRASER. 15
found to be almost universal in Australia. The symptoms in the most severe form of the disease include pitting of the trunk and branches with deep furrows, often somewhat contorted (small furrows or pits can occasionally be seen on young twigs if the bark is removed), reduced vigour, poor growth and fruit which are reduced in size, flattened or lopsided and thick-skinned. Symptom expression is, however, extremely variable, sometimes one growth feature predominating, sometimes another, so that in the field trees are encountered which have deeply pitted contorted trunks but with reasonably good fruit, others with a high proportion of very poor fruit and little or no visible pitting. Many variations and combinations of symptoms occur. The test seedling used for indexing for the presence of this virus is the West Indian or Key lime (McClean, 1950). On this the virus produces small pits or furrows on the xylem surface and flecks or cleared areas in the veins of the leaves. The identification of the virus causing symptoms in lime with that causing the disease of grapefruit is based on the fundamental similarity of the symptoms and on the fact that inoculation from limes back to virus-free grapefruit seedlings reproduces symptoms of stem pitting and fruit distortion in them. Using the West Indian lime as an indicator, surveys of New South Wales citrus have shown the stem pitting virus to be far more widespread than the visible symptoms would suggest. Many completely symptomless grapefruit produced when inoculated on lime seedlings a mild type of pitting and occasional vein flecks. It is assumed from this that there are strains of stem pitting virus so mild that no field symptoms sre produced by them even in the most susceptible varieties. Also, on the basis of the lime reaction, it has been determined that the stem pitting virus is present in New South Wales in all citrus of all varieties except Poncirus trifoliate and some of its hybrids, with the exception of a number of orange and grapefruit trees in south-western New South Wales propagated from the original Chaffey introduction. In this area, however, the disease is spreading and its progress is being watched in a number of grapefruit groves.
Most citrus varieties carry the disease quite symptomlessly. In Australia symptoms of pitting are only produced on grapefruit and rarely on smooth Seville orange and Bengal citron.
The severity of symptoms produced in indicator seedlings of West Indian lime varies considerably. Buds from symptomless grapefruit produce, in all cases indexed, the mildest reaction encountered on lime. In general the most severe reactions are obtained from trees showing the severest pitting and stunting, but the correlation is not exact. It is possible that this could be explained by the presence of a number of different strains in the one tree. :
No direct control measures are possible for a disease of this nature. The perennial host, the widely distributed virus and the ubiquitous vector make protection from infection impossible and it is only a matter of time before all grapefruit trees in New South Wales will be infected. The question therefore arises, can grapefruit be successfully produced in Australia in the future? Two possible means are being investigated: (1) the location of a grapefruit variety which is not damaged by the presence of the virus, i.e., a tolerant type, and (2) mild strain protection. In many viruses the presence of one strain delays or prevents the establishment of a second strain of the same virus. Whether this is practicable for a perennial crop constantly subjected to reinfection can be determined only by field experiment. The possibility of mild strain protection for a perennial crop was investigated by Posnette (1947) in the case of cocoa swollen shoot virus but he reported only partial success with the method.
Relationship between Tristeza and Stem Pitting.
Proof of the virus nature of tristeza was first obtained by using as test plants budded trees of sweet orange on Seville orange rootstocks (Fawcett and Wallace, 1946; Meneghini, 1946). Later, Costa et al. (1950), using a range of seedling and budded trees, obtained on lime the reaction of vein flecking and pitting described by McClean (1950) as a reaction to infection by stem pitting virus. They suggested that this reaction was also that of tristeza, and as a corollary that tristeza and stem
16 VIRUS DISEASES OF CITRUS IN AUSTRALIA,
pitting are different effects of the one virus. This has been generally accepted, and the lime reaction has been used to index citrus for the presence of tristeza in many parts of the world.
During the course of a survey of citrus in New South Wales, using a range of seedling varieties as indicators, a type of reaction was found which appeared to be quite distinct from the vein clearing, pitting reaction on lime. It was obtained with buds from oranges, mandarins, rough lemon, Rangpur lime and some tangelos and calamondin. When these were inoculated to Seville orange, grapefruit, lemon and citron seedlings, there was produced very severe reduction of growth, yellowing and, in the scion, a yellow tristeza-like effect. This was considered to be a distinct virus from that causing the lime reaction and it was named seedling yellows (Fraser, 1952). The lime reaction virus was present as well in all trees indexed and it has not yet been possible to separate yellows from this virus. The same reaction had been seen by Costa et al. (1949) but not considered to be different from the lime reaction. Mature trees of grapefruit, lemon, Seville orange and some other varieties have never been found to be infected with the yellows virus and appear to be susceptible to infection only as very young seedlings. As pointed out by McClean and Van der Plank (1955) the yellows reaction is undoubtedly a tristeza reaction. This at once brings into question the status of the stem pitting and vein flecking reactions of lime. A number of theories have been put forward.
Costa (1956), Knorr and Price (1957), and others regard the West Indian lime reaction as a symptom of tristeza virus and yellows as an associated symptom. McClean and Van der Plank (1955) and McClean (1956) put forward the view that tristeza disease has two components, yellows and stem pitting, and that these are most probably related strains of one virus. Wallace (1957) holds somewhat similar views.
Results of experimental work in New South Wales favour the view that the seedling reaction of yellows and that of stem pitting and vein flecking are caused by distinct viruses. Virus isolates of stem pitting alone do not cause a tristeza type of decline when inoculated into grafted seedlings composed of sweet orange top and Seville orange rootstock. The most severe strains, obtained from grapefruit trees showing strongly developed symptoms of pitting, stunting or fruit distortion, reduce the vigour of growth of such indicator trees but do not cause the characteristic yellowing and deterioration of the scion. The mildest strains of stem pitting do not reduce vigour, and strains of intermediate virulence have an intermediate effect on vigour of indicator trees.
When, however, buds containing the yellows-producing virus are used to inoculate indicator trees of sweet orange on Seville orange rootstocks, the scion ceases to grow, turns yellow and ultimately dies. These reactions appear to be distinct, and the direct reactions of seedling indicators also appear to be distinct and without inter- grading forms to suggest they are related.
It is considered, therefore, that the lime reaction of vein clearing and xylem pitting is a seedling reaction to stem pitting virus and should not be used without corroboration as a test for the presence of tristeza disease in a citrus community.
The use of the word virus complex by McClean (1956) and McClean and Van der Plank (1955) carries the implication that both components contribute to the severe tristeza reaction. There is, however, no evidence available which can cast any light on this question and the solution must await the separation of yellows from admixture with stem pitting.
Viruses Not Known to be Present in Australia.
Stubborn.—This disease was described first by Fawcett (1946) in California. Grape- fruit and orange varieties, particularly Washington navel, are affected. Trees lack vigour, fruit is small and sometimes misshapen, often with the rind at the distal end thinner than that at the stalk end.: Symptoms are somewhat variable; not all the fruit on an affected tree show symptoms each year. The foliage is somewhat chlorotic, growth is short and affected with die-back and the development of multiple buds gives a bushy appearance to the trees. The disease is widespread also in
BY LILIAN R. FRASER. 17
Morocco and possibly other Mediterranean citrus growing countries. No satisfactory indicator is known and the disease may take a considerable time to develop.
Xyloporosis.—The virus disease first observed in Palestine in 1928 (Reichert and Perlberger, 1931) affects particularly the sweet lime, both as an unworked seedling and as a stock for sweet orange and other varieties (Reichert et al., 1953).
The symptoms on sweet lime are as follows: Pits develop on the xylem surface of the wood of the stock. These are rounded or conoid in shape and have corresponding pegs on the bark inner surface. A brown discoloration occurs in the bark. As the disease progresses the wood becomes impregnated with gum, bark cankers develop and the tree ultimately dies.
Growth of sweet orange on this stock is poor, with considerable dieback, leaves are small, upright and yellowish. Xyloporosis also occurs in South America (Fawcett, 1937; Knorr et al., 1952) and is common and widespread in Florida, where it affects principally the Orlando tangelo, mandarins and kumquats, but is symptomlessly carried in grapefruit and orange varieties (Childs, 1952).
Xyloporosis and stubborn disease have nothing in common and there seems to be no possibility that they are related, yet different aspects of the grapefruit stem pitting disease have something in common with each.
The problem of separating and identifying these different viruses should all be present in the citrus community offers great difficulty particularly in the case of stubborn, for which no satisfactory indicator has yet been found.
Future Outlook.
The means which have to be adopted to safeguard the citrus crops of Australia from inroads by virus disease are of several kinds.
1. Where the virus has no known insect vector and is spread by the use of infected budwood it is necessary to ensure that material used in propagation is virus-free. The diseases which fall into this category are psorosis and scaly butt. The principal bark symptoms of psorosis may not become apparent for many years, but the associated foliage symptom is evident from the earliest stage. Seedlings inoculated with psorosis-infected budwood develop these symptoms and so a means is available of checking the health of budwood sources. Symptoms of scaly butt and associated stunting of P. trifoliata take two to eight years to develop, possibly longer in some cases. Trees on this stock, more than eight years of age, of good vigour and stock character, can be assumed to be free of scaly butt virus, and can safely be used as a source of budwood. There are some varieties, however, of which no suitable trees on P. trifoliata are known, and in order to obtain scaly butt free budwood the only course as yet available is to index a number of selections onto P. trifoliata and grow the trees until they are old enough to produce symptoms.
Lemon crinkly leaf appears also to fall into the category of diseases which can be eliminated by the use of virus-free budwood taken from trees free of symptoms, and if necessary indexed onto seedling lemons.
2. Where an active insect vector and a reservoir of virus are present no purpose is served by the use of virus-free propagation material. The presence of the virus must be accepted and its effects minimized if possible. In the case of tristeza, control is achieved by the use of non-susceptible scion-stock combinations. .In the ease of stem pitting, where the most susceptible variety is also a favoured commercial one for which no substitute is at present available, the only hope seems to lie in the possibility of mild strain protection.
The enation and woody gall viruses would appear to be of such slight importance that no action against them would be justified.
The introduction of citrus varieties from overseas poses a difficult problem for the pathologist. To ensure that no new disease is brought into the country all intro- ductions should be tested for the presence of all known viruses. This would take a considerable time and would involve more expense than is justified for the results obtained, and might still permit tbe entry of undescribed or unknown viruses. For in addition to those which are known, there are the host of disorders which are not
B
18 VIRUS DISEASES OF CITRUS IN AUSTRALIA,
yet proved to be, but almost certainly are, virus in nature. Hach may be unimportant from a world standpoint, but is perhaps Jocally important, or potentially so if disregarded.
There are, however, ways of eliminating virus infections from plant material. With one exception (Xyloporosis, Childs, 1956) citrus viruses are not known to be seed-borne, so that seed can safely be introduced. Most citrus varieties produce a proportion of nucellar seeds, so that by careful selection of seedlings, types closely approximating to the parent can be obtained. There are, however, some varieties which produce no nucellar seed, and others with particular agronomic qualities which are not transmitted to their nucellar offspring. For such varieties the possibility of elimination of virus infection by heat therapy holds some promise. Grant (1957) has recently shown that psorosis virus can be eliminated by growing an infected plant at a continuously high temperature for three months or more and it is possible that further investigations will show that other viruses may similarly be eliminated, perhaps paving the way for the development of a standard treatment which could be given to imported material to eliminate the hazard of importing disease as well. A third and perhaps even more promising line of attack is based on the fact that the embryonic tissue of the growing point is not invaded by virus. It has already been shown that for some plants propagations from growing tips will eliminate virus disease. This possibility should certainly be explored for citrus viruses also.
Literature Cited.
ALDERTON, G. E., 1884.—Treatise and Handbook of Orange Culture. Auckland, New Zealand. BENNETT, C. W., and Costa, A. S., 1949.—Tristeza Disease of Citrus. Journ. Agricultural
Research, 78: 207-237.
BENTON, R. J.. BowMAN, F. T., FrAspr, L., and Keppy, R. G., 1950.—Scaly Butt and Stunting of Citrus. Dept. Agriculture N.S.W., Science Bulletin No. 79.
—— ; , 1952.—Significance of Trifoliata for Citrus Rootstock Problems. Report of the 13th International Horticultural Congress, Vol. 2: 1235-40. BowMan, F. T., 1956.—Citrus-Growing in Australia. Sydney.
CHILbs, J. F. L., 1952.—Cachexia Disease, its Bud Transmission and Relation to Xyloporosis
and to Tristeza. Phytopath., 42: 265-268.
, 1956.—Transmission H!xperiments and Nyloperosis-Cachexia Relations in Florida.
Plant Disease Reporter, 40: 143-145.
Costa, A. S., 1956.—Present Status of the Tristeza Disease of Citrus in South America.
F.A.O. Plant Protection Bulletin, 1V: 97-105.
Costa, A. S., GRANT, T. J.. and Moreira, S., 1949.—Investigacoes sobre a tristeza des citrus,
Il. Bragantia, 9: 59-80.
—- ; ——, , 1950.—A Possible Relationship between Tristeza and the Stem-
pitting Disease of Grapefruit in Africa. Calif. Citrog., 35: 504, 526-528.
Fawcett, H. S., 1936.—Cilrus Diseases and their Control. New York. , 1937.—Contacts with the Citrus Industry and other Observations in South America.
Calif. Citrograph., 22: 552-5538, 571-572, 575.
, 1946.—Stubborn Disease of Citrus, a Virosis. Phytopath., 36: 675-677. Fawcett, H. S., and Birancourt, A. A., 19438.—Comparative Symptomatology of Psorosis
Varieties on Citrus in California. Phytopathology, 33: 837-864.
Fawcert, H. S., and Kuorz, L. V., 1948.—Bark Shelling of Trifoliate Orange. Calif.
Citrograph., 33: 230.
Fawcert, H. S., and WaAuLacn, J. M., 1946.—Hvidence of the Virus Nature of Citrus Quick
Decline. Calif. Citrograph., 32: 50, 88-89.
FrAseR, L. R., 1949.—A Gummosis Disease of Citrus in Relation to its Environment. Proc.
LINN. Soc. N.S.W., 74: 5-18.
, 1952.—Seedling Yellows, an Unreported Disease of Citrus. Agr. Gaz. N.S.W.,
63: 125-131.
Grant, T. J., 1957.—Effect of Heat Treatments on Tristeza and Psorosis Viruses in Citrus.
Plant Disease Reporter, 41: 2382-234.
Knorr, L. C., and BENATENA, H. N., 1952.—Xyloporosis en Mandarino Comun de Concordia.
Idia, 5: 19-20.
Knorr, L. C., DuCHARME, EH. P., and BAnri, A., 1951.—Exocortis in the Citrus Groves of
Argentina. JIdia, 4: 8-12.
Knorr, L. C.. DuCHARME, EH. P., and Buspy, J. N., 1954.—Discovery of Exocortis in Florida
Citrus. Plant Disease Reporter, 38: 12-138.
Kxnorr, L. C., and Price, W. C., 1957.—Is Stem Pitting of Grapefruit a Threat to the Florida
Grower. Citrus Industry, 38: 11-14.
BY LILIAN R. FRASER. 19
McALPIN, D. M., Parsal, P. S., Ropprts, R., and Hopr, R. H., 1948.—‘*Bud Union Decline” Disease of Citrus. Journ. Dept. Agric. Victoria, 46: 25-31.
McCLeAN, A. P. D., 1950.—Virus Infections of Citrus in South -Africa III. Stem Pitting of Grapefruit. Farming in South Africa, 25: 289-296.
—————, 1954._Citrus Vein Mnation Virus. S. Afr. Jour. Sci., 50: 147-151.
, 1956.—Tristeza and Stem-pitting Diseases of Citrus in South Africa. F.4A.0. Plant
Protection Bulletin, 4: 88-94.
——, 1957.—Virus Infections of Citrus Trees. Jbid., 5: 133-141.
McCLEAN, A. P. D., and VAN DER PLANK, J. H., 1955.—The Role of Seedling Yellows and Stem Pitting in Tristeza of Citrus. Phytopath., 45: 222-224.
Mackay, A., 1875.—The Australian Agriculturist.
MENEGHINI, M., 1946.—Sobre e natureza e transmissibilidade “da doenca’’ ‘‘tristeza’” dos citrus. Biologico, 12: 285-287. Moreira, S., 1955.—A molestia “Exocortis’’ e o cavalo de limoeiro cravo. Rev. Agric.,
Piracicaba, 30: 99-112.
OBPRHOLZER, P. C. J., MatTHews, I., and STipMin, S. F., 1949.—The Decline of Grapefruit Trees in South Africa. A Preliminary Report on So-called Stem-pitting. Union S. Afr., Dept. Agr. Sci. Bulletin, 297.
OLSEN, H. O., and SHuLL, A. V., 1956.—Hxocortis and Xyloporosis—Bud Transmission Virus Diseases of Rangpur and other Mandarin-Lime MRootstocks. Plant Disease Reporter, 40: 939-946.
Posnette, A. F., 1947.—Virus Diseases of Cacao in West Africa. Ann. Appl. Biol., 34: 388-402.
Pys, T., 1890.— Bull. No. 1, N.S.W. Dept. Agriculture.
REICHERT, I., and PERLBERGER, J., 1931.—Xyloporosis, the New Citrus Disease. Hadar, 7: 163-167, 172, 183-202.
REICHERT, I., YORPFE, i., and BENTAL, A., 1953.—Shamouti Orange on Various Rootstocks and its Relations to Xyloporosis. Palestine Journ. Botany, Rehovot series, 68: 163-183. Reitz, H. J., and Knorr, L. C., 1957.—Occurrence of Rangpur Lime Disease in Florida and
its Concurrence with Exocortis. Plant Disease Reporter, 41: 235-240. Rossetti, V., 1955.—A doenca do lomoeiro eravo nos laranjais de Sao Paulo. Biologica,
21: 1-8. WALLACH, J. M., 1957.—Tristeza and Seedling Yellows of Citrus. Plant Disease Reporter. 41: 394-397.
—, 1956.—Tristeza Disease of Citrus, with Special Reference to its Situation in the United States. F.A.O. Plant Protection Bulletin, 4: 77-87.
WALLACE, J. M., and DRAKE, R. J., 1951.—Newly Discovered Symptoms of Quick Decline and Related Diseases. Citrus Leaves.
————_, ——_—,, 1953.—New Virus Found in Citrus. Calif. Citrograph., 38: 180.
WALLACE, J. M., OBERHOLZER, P. C. J.. and HormMryer, J. D. V., 1956.—Distribution of Viruses of Tristeza and other Diseases of Citrus in Propagated Material. Plant Disease Reporter, 40: 3-10.
WEBBER, H. J., 1943.—The “Tristeza’’ Disease of Sour-orange Rootstock. Amer. Soc. Hort. Sci., 43: 160-168.
BB
20
SEED COAT ANATOMY AND TAXONOMY IN HUCALYPTUS. L. By EH. GAaurga and L. D. Pryor. (Plate i; nineteen Text-figures.) [Read 26th March, 1958.]
Synopsis.
Anatomical and histochemical investigations of the seed coat of Blakely’s two Renantherous Sections of Hucalyptus aimed at revising these groups show for the bulk of the species a remarkable consistency. The seed develops from an anatropous, bitegmic, crassi-nucellate ovule. The salient testa characters are: the outer integument is several layered, with its outer epidermis built up by sclereids, its inner epidermis crystal-bearing but without forming a typical “crystal epithelium”; the inner integument persistent, two-layered and suberized. An elaborately ramified vascular system extends from the basal hilum to the distal chalaza.
However, three of Blakely’s series, Ochroxylon, Steatoxylon and Myrtiformes, deviate considerably from each of these testa features and vascularization pattern and probably are not correctly placed in the Renantherae.
INTRODUCTION.
Since Bentham’s (1866) original treatment the taxonomy of Hucalyptus has been based on various characters of the anther, such as shape, mode of dehiscence, attachment to the filament and relative position of the gland. It has been obvious more recently that some of the groups formed on this basis are not homogeneous. It has now been found that the anatomy of the seed coat, together with some morphological ovule and seed characters, promises to give valuable data for a regrouping of some species.
The value of the study of seed coat anatomy is not confined to its application to taxonomy, since it is likely also that seed coat structure and seed behaviour are related.
Blakely’s “Key to the Hucalypts” is the most recent classification of the genus, and undoubtedly the most satisfactory yet published. In such a large genus, however, it is to be expected that even in so excellent a work there will be anomalies in the arrangement of some of the species, and at different times some of these have been suggested by investigations carried out in other ways. For example, Blake (1953) has shown on general morphological grounds how the species belonging to the Clavigerae as understood by him form a natural group, but in Blakely’s ‘‘Key” they are partly separated. It has also been suggested (on the grounds of cotyledon shape) that some species having bisected cotyledons and separated by Blakely in his “Key” would more appropriately be placed together in the same taxon (Pryor, 1956).
Amongst all of Blakely’s groups, however. the combined group Renantherae and Renantherae-Normales, containing about 100 species, is one which possesses a high degree of homogeneity, and it seems clear that this group, largely as defined by Blakely, might well be constituted a subgenus.
It was already known at the time this investigation began that in morphological characters the seed of the great majority of species within this composite group had features in common but at the same time these were to be seen seldom in species placed by Blakely in other sections. It seemed likely, therefore, that this group would be essentially a natural unit. It followed, therefore, that if a similar uniformity were found in seed coat anatomy this would conform with this view. Further, if among the species thus placed together by Blakely occasional exceptions to the common ‘pattern of seed coat structure were found, it might be deduced that these were incorrectly included in the group. At this point, therefore, it appeared that an examination of seed coat structure would be profitable and the study was commenced.
PROCEEDINGS OF THE LINNEAN Society oF NEw SoutTH WaArTKES, 1958, Vol. Ixxxiii, Part 1.
BY E. GAUBA AND L. D. PRYOR. 2
The seeds used in this investigation were mostly the result of our personal collection, but some which were either rare or difficult to collect were obtained from different State Forestry Departments, Botanic Gardens and Herbaria, to which we are indebted for generous assistance. In a few cases seed from commercial sources has been used.
The microscopic sections were made by hand without prior preparation, and the drawings with a camera lucida.
Blakely (1955) has been followed in nomenclature and systematic grouping.
The purely anatomical aspects of the investigation considerably extend our knowledge in this field of research on Hucalyptus. They have been linked with previous publications on the subject, not all of which have been fully correct. ‘There has been no previous reference in the literature to the taxonomic implications of seed coat anatomy in Hucalyptus, and the conclusions in this regard are arrived at entirely from the present work.
In the following, “testa” is taken to mean the seed coat derived from both seed integuments. Published work on the anatomical structure of the Hucalyptus testa has. up to the present been quite limited. In an extensive work, Petit (1908) investigated the structure of 14 genera of Myrtaceae, including 59 species in the genus Hucalyptus. However, he gave emphasis principally to the anatomical structure of the fruit wall, both torus and pericarp, rather than to the seed coat. Only in 10 species was the testa also examined, and of these four species alone were illustrated. One of these, Hucalyptus macrocarpa (Fig. 22, page 51) is erroneous, illustrating, most probably, the testa of one of the species of the Renantheraet The remaining nine species all belong to the Section Macrantherae, sc that Petit’s work does not give a balanced presentation of the distinct diversity of testa structure in the genus Hucalyptus. Raphe, chalaza and the course and structure of the conducting tissue were not investigated. Nor were the wall substances microchemically tested, so that the very interesting presence of an inner cuticle and of suberized tissues in the seed coat (with their physiological implications) escaped him.
Netolitzky (1926) gives a detailed and penetrating summary of seed structure for any work dealing with seed anatomy. The author records all facts known at that time and adds the results of his own critical studies. In particular with regard to Hucalyptus he reports generally the results of Petit’s work and reproduces also, amending the annotation, three of his figures, H. calophylla, E. globulus and #. “macrocarpa”’. Harada (1956) has examined in no great detail ten Hucalyptus species, but inaccuracies of observation and conclusion impair the value of the publication.’
In the fundamental works of Ferdinand von Mueller (1879) and J. H. Maiden (1929), figures and descriptions of seed are presented purely from the morphological viewpoint. Maiden gives a classification of seed according to colour, size, surface structure, position of hilum and similar features. Some of these characters are better understood, as will be seen later, if interpreted anatomically.
In addition we shall refer to other specific relevant points in the literature as they arise.
Finally it may be said that, no matter how important the role of anatomy may be in providing clues for taxonemic relationships, we are conscious of the fact that anatomical features alone (and from one part of the plant only) cannot lead to final conclusions until they are supported by evidence, especially morphological, from other parts. However, characters like testa structure and the vascularization pattern of the seed are features fixed by deep-seated factors of inheritance and scarcely affected by environmental factors. Therefore they may provide valuable facts for the establishment of taxonomic affinities.
1 This view results from the study of seed collected ourselves from H. macrocarpa growing naturally near Wagin, Western Australia.
2Harada appears to be unaware of the precise delimitation of the two integuments. Several times he presents only the outer epidermis as the outer integument, and designates in text and figures the subepidermal parenchyma of the outer integument as the inner integument. In surface sections he speaks of a “network of strips’ without realizing that these are cross-sections of anticlinal epidermal cell walls.
22 SEED COAT ANATOMY AND TAXONOMY IN EUCALYPTUS. I,
SECTION RENANTHERAE-NORMALES.
The Outer Integument of the Ripe Seed.\—This is composed of several layers. The outer epidermis is made up of a solid layer of sclereids with secondary, lamellated thickenings on the outer and radial walls, the latter traversed by corresponding simple or ramiform pit canals. ‘The excessively centripetally thickened walls leave a very small lumen. They are mostly lignified, and this very strongly so in H. triantha, HE. laevopinea, EH. macrorrhyncha, E. alpina and others, but no phloroglucin reaction was obtained in H. haemastoma, indicating the absence of lignin. The size of the epidermal cells is variable in one and the same seed. At the edges and ribs and around the hilum the height of these epidermal cells can be many times the breadth (macrosclereids). On the flat side of the seed they are more or less isodiametrical or even frequently elongated parallel to the surface of the seed. They are relatively small-in #. stellulata (Pl. i, fig. 4) and #. salicifolia, and by comparison very large in #£. planchoniana, EH. laevopinea (Pl. i, fig. 1) and others. The outer cuticle is missing, or at the most just discernible as fragmentary remnants as in EZ. oreades, HL. kybeanensis, H. stellulata and #. piperita. The inner epidermis is made up of small, thin-walled tabular cells. The number of layers of parenchymatous cells between the two epidermal layers changes not only with the species but also with the position on the seed at which the examination is made, that is to say, at ribs and corners, and particularly along the raphe there is always a iarger number than on the flat side of the seed. There are a few layers only in #H. sparsifolia, B. salicifolia and EH. oreades (two to three), and they are numerous in H. planchoniana (six te eight).
lr Monoclinic crystals of primary calcium exalate monohydrate (identical with the mineral whewellite) occur dispersed in the cells of the outer integument (excluding the outer epidermis). They are most plentiful in the raphe parenchyma just over the hilum, where they are arranged in vertical files accompanying the vascular bundle (Text-fig. 4). They are often also more numerous in the ribs. There is special significance in their localization in the inner epidermis.* In some species (H. piperita, #H. pilularis, EH. planchoniana) they are missing or extremely rare on the raphe-free sides. In #H. stellulata they occur only in the lower part of the seed. In #H. salicifolia their occurrence is patchy. They are small and scarce in #. oreades but scattered over the whole raphe-free sides. They are abundant in #. macrorrhyncha (Text-fig. 5) and #. haemastoma (Text-fig. 1). In #H. sparsifolia nearly every epidermal cell accom- modates a large, well-developed crystal. In H. muelleriana many of the crystal-bearing cells have irregular, uneven wall thickenings which partly surround the crystals or enclose them completely (Text-fig. 2). Furthermore, some of these crystals in the hilar region have an additional cellulose membrane as an envelope (Text-fig. 3).
This discontinuous presence or complete absence of calcium oxalate crystals in gererally unmodified cells of the inner epidermis of the outer integument is likely to have taxonomic significance. As will be indicated later, this epidermis in other sections of the genus is formed of cells strongly thickened at the base, each carrying one or more crystals. In the Angiosperms the occurrence of this “crystal epithelium”’ is widely distributed, especially in the more primitive families, and is generally considered in the phylogenetic sense as a primitive character. Within the Renantherae the inner epidermis has, to a greater or lesser extent, lost its character as a “crystal epithelium’’.
8 Strictly, one ought to speak of the derivative of the outer integument, but to simplify discussion we shall refer to the two parts forming the seed coat as inner and outer integument.
4Tsolation of the inner epidermis exposing larger areas is necessary to obtain correct information about their distribution. It is also important to compare raphe-free sides above the hilar region because crystals are always present in the vicinity of the bundle, hilum and micropyle.
5 Blakely’s Series Pseudo-Stringybarks comprises three species: EH. pilularis, which we found erystal-free, H. muelleriana, where about half of all epidermal cells are crystal-bearing, and E. wardii. Of the last-named we had only a few seed fragments from the holotype for examination, revealing about the same frequency of crystals in somewhat irregularly thickened eells as in H. muelleriana, though in a lesser degree. The hilar region could not be investigated.
BY E. GAUBA AND L. D. PRYOR. 23
As a whole the outer integument represents the “pigment layer’, and the ripe seed displays, due to this, a brown to black colouring. There are dark-coloured compounds, giving tannin reaction,® impregnating the walls and filling as amorphous deposits the lumina of the epidermal cells, the parenchyma and the chalaza cork tissue (Text-fig. 18). They are probably closely related to the phlobaphenes (anhydrides of tannin) of the bark. In the White Mahoganies (#. triantha and EH. carnea) impregnation of the walls of the outer epidermis is weak or even absent. On thin sections they appear ivory white and give a strong phloroglucin reaction which is partly masked in other species, due to the brown colouring by tannin impregnation.
As the result of this study of the structure of Hucalyptus seed we consider the raphe as part of the outer integument and not—as it still is described in some recent literature—as the fusion of the funicle with the testa. The parenchyma and the epidermis of the raphe have the same structure and contents as the rest of the outer integument. Thus in the Renantherous seed coat the same sclereid epidermis covers the raphe as well as the remainder of the seed. Where the inner wall of the outer epidermis cells is mucilaginous, as in H. marginate, or where palisade-like thin- walled epidermal cells filled with solid dark-coloured material occur in other systematic groups (#. maculata, H. citriodora) we find them also unchanged over the raphe in wall structure and zontents.
The hilum is a clearly seen sear surrounded by a raised rim of sclereids. There is no protective layer covering the exposed surface, which is neither cutinized nor suberized, nor covered by a cuticle. Thus the exposed cells wear away, the surface breaks up and in the course of time the hilum becomes more or less hollowed and air-filled. This may rather retard than facilitate the intake of water for germination.
From the hilum an amphicribral vascular system with helically thickened tracheids extends in the expanded raphe parenchyma right up to the chalaza (which is not externally visible) where it finally spreads out (Pl. i, figs. 3, 4, and Text-fig. 19, 1). Integumentary buné@les, i.e. a system of strands branching off the raphe bundle and traversing the outer integument, do not exist.
The Inner Integument—This occurs immediately below the outer integument. In ripe seeds the median cuticle delimiting the two integuments is resorbed. In the genuine Renantherae the inner integument is two-layered, being formed of both epidermal layers alone. The cells are tabular and without intercellular spaces. In contrast with species in Blakely’s two series, Steatoxylon and Myrtiformes, in all remaining series of the Renantherae-Normales this integument has not been resorbed in the course of ripening. It is suberized‘ throughout (PI. i, figs. 1, 3, 4), the walls being not merely impregnated with fatty substances. If after previous treatment with Eau de Javelle, tests are made with zinc chloroiodide, brown-coloured delicate suberin lamellae separate themselves from the primary cellulose walls which appear blue- coloured. The walis are in addition more or less impregnated with tannin-like material.
The shape and size of the micropylar end of the inner integument vary considerably within the same species. There is either a biunt or pointed tip without any sign of an aperture, or the apex is lengthened to form a cylindrical or conical tube, the endostome, with a straight or somewhat funnel-like dilated rim. The capillary canal is blocked by reddish-brown material which also fills the surrounding cells (Text-figs. 8, 9, 10 and 11). Thus there is little chance of an appreciable intake of water or nutrients through the endostome to the embryo once the suberization is completed.*
®The microchemical test for tannins in the wide sense of the term (which comprises very different substances) is generally limited to ferric salts staining green or blue. This of course does not reveal much about the precise nature of these compounds.
7 Besides the fat-staining compounds which can give ambiguous results, Hoehnel’s cerin acid reaction was used to test the suberin lamellae.
§The exostome is occluded, most of the species showing—sub lente—a faint short fissure or ridge between hilum and the micropylar region which could be considered perhaps as the exostome suture. However, this needs further investigation. But in view of the fact that moisture is readily absorbed by the whole cuticle-free epidermis it is of secondary importance for germination as to whether or not the intake of water is effective through hilum and micropyle.
24 SEED COAT ANATOMY AND TAXONOMY IN EUCALYPTUS. I,
Netolitzky’s opinion is that the main role of cork tissues and cuticles in Angiosperm seed coats lies in the prevention of emigration of crystalloids (formed by mobilization of the colloids during germination) from the embryo.
8 3 10 11 Text-figs. 1-11.
1-7: Monoclinic crystals of caicium oxalate monohydrate, ca. 180x.
Fig. 1, 2, 5, 6, 7: crystal-bearing inner epidermis of the outer integument in surface view. 1: Eucalyptus haemastoma; 2: H. muelleriana; 5: H. macrorrhyncha; 6: E. brachyandra, the crystal epithelium is seen iying beneath the outer epidermis; 7: H. guwilfoylei, the crystal epithelium is viewed from the inside of the seed. Through the gap (g) in the erystal layer (in the chalaza region) the tracheary endings (¢) of the raphe bundle are seen.
Fig. 3: H. muelleriana, crystals with cellulose envelopes in thick-walled cells.
Fig. 4: #. muelleriana, crystals in short files accompanying the raphe bundle.
8-11: Some endostome forms, ca. 180x. 8: Bucaiyptus muelleriana; 9: EH. oreades; 10: #. salicifolia; 11: H. gigantea. The forms are variable within the same species.
At the inner limit of the inner integument (and therefore of the testa in general) an inner cuticle is encountered which is rather conspicuously developed and forms rib-like projections between the nucellus epidermal cells (Pl. i, fig. 1), so that in
BY E. GAUBA AND L. D. PRYOR. 25
surface view this cuticle simulates cellular structure. It is the product both of the inner integument and nucellus where their surfaces are in contact, and therefore of double origin. However, the formation of this cuticle is suppressed in the chalaza region.
The chalaza is reckoned also as part of the testa. It is the parenchymatous tissue where nucellus and integuments merge. It is the pathway for nutrients to the integuments and through the gap in the inner cuticle to the embryo and its associated tissue. Once the supply to the embryo is completed this gap is closed by suberization of neighbouring chalaza tissue and by filling the cork cells with dark-coloured solid material (PI. i, figs. 3 and 4). The suberization is of the type of the inner integument, therefore there is an inner suberin lamella alongside the cellulose wall. It must be noted, however, that this “chalaza cork” is not of uniform origin, because not only do the cells of the chalaza sensu stricto undergo suberization, but partly the neigh-
14
Text-figs. 12-18. 12-13: Diagrams of germinating seed. 12: Hucalyptus dives; 13: EH. microcorys — cd, clinging disc; ch, chalaza cork; cr, crystal layer; h, hilum; hy, hypocotyl; ic, inner cuticle; m, micropylar region; 7, radicula; vb, vascular (raphe) bundle.
14-17: Chaff structure. 14: H. iaevopinea, transy. section; 15: H. microcorys, transv. section of chaff with ventral hilum; 16: EH. microcorys, transv. sec. of chaff with basal hilum: 17: E. guilfoylei, tang. sect. of outer epidermis of.chaff with ventral hilum showing the blind pits in the outer wall.
18: EH. fraxinoides, transv. sect. of the cuter integument, the phlcbaphene-bearing cells (pigment layer) shaded. All sections ca. 180x.
bouring tissue of the nucellus is also involved—often, indeed, the latter forms the major portion of the whole “chalaza cork’. Furthermore, the suberization extends also into the raphe parenchyma and adjoins the suberized inner integument (PI. i, fig. 4), forming finally (in surface view) a large circular, oval or elliptical, dark- coloured disc above the smaller cuticular gap. With some care it is possible to extract the inner integument with the adherent chalaza cork revealing its size and shape.
It is beyond the limits of the present study to make an extended histochemical and structural investigation of the embryo and its supporting tissues and the alterations they undergo during the maturation of the seed. It seems, however, that nucellus and endosperm also in some circumstances can throw light on taxonomic relationships.
26 SEED COAT ANATOMY AND TAXONOMY IN EUCALYPTUS. I,
Therefore a few remarks about the final stage of these parts as seen in the mature seed are justified.
In the resting seed there is a more or less broad remnant of the nucellus tissue, especially in the chalaza region, the cells of which are empty and largely obliterated so that without application of swelling media the cellular structure in general cannot be distinguished (PI. i, figs. 1, 3, 4). The endosperm is resorbed, except in the micro- pylar region, where an intact layer one cell thick and rich in proteins is retained (2. muelleriana, H. alpina, H. sparsifolia, H. planchoniana, EH. oreades and others). Testing the germination residue of H. planchoniana with Millon’s or Raspail’s reagent reveals that these proteins have not been used during the germination. They represent a reserve surplus.
Finally, the embryo is itself covered by a cuticle which, however, does not at this stage form a tough skin but rather a semisolid envelope on which oil drops from the embryo dislocated by sectioning remain attached. In the resting seed, therefore, it has not reached its final consistency and it separates easily from the embryo epidermis. The seed being exalbuminous (without endosperm) the food reserves for germination are stored in the large embryo (cotyledons and hypocotyl) which fills completely the cavity enclosed by the seed coat. Storage substances are fats (in the form of oil droplets) and proteins (aleuron grains) .®
With the exception of the two series Steatoxylon and Myrtiformes the testa structure described above is uniform in principle in all the series and subseries of the Renantherae-Normales, almost all of which have been investigated.° In these groups the following species were examined: H. pilularis, H. muelleriana, EL. umobra, HE. triantha, E. laevopinea, EH. macrorrhyncha, H. alpina, EF. sparsifolia, E. obliqua, E. gigantea, EH. planchoniana, E. oreades, HE. fraxinoides, H. kybeanensis, HE. pauciflora, E. stellulata, EH. salicifolia, H. dives, H. tasmanica, HE. piperita and H. haemastoma. ‘There is little doubt in assuming that Blakely’s categories, series and subseries, are essentially homogeneous. On this basis, therefore, the material examined satisfactorily represents 94 species.
In summary, the following points are distinct and characterize the testa of the Renantherae-Normales:
1. The outer integument consists of several layers, its outer epidermis is formed of sclereids, its inner epidermis does not form a specific crystal layer. 2. The inner integument persists, is two-layered and suberized. Whether this structure is exclusively confined to this group of Hucalyptus and may be used as an index of relationship or whether it appears also in other systematic groups as the result of convergent development will not be fully apparent until the investi- gation of all the remaining sections in the genus is complete. For the moment we are able to point out that, for example, the testa of #. patens and EH. diversifolia (Sect. Renantheroidae) and that of H. jacksoni (Sect. Macrantherae) are in all histological and morphological details precisely that of the pattern in the Renantherae-Normales.4 Relating structure with function of the seed coat, it is obvious that the closely- packed epidermal sclereids confer high mechanical protection, while the biological function of the tannin deposits in the outer integument no doubt lies first of all in the chemical protection against decay. The strongly reduced permeability resulting from the suberized tissues (inner integument, chalaza) and the inner cuticle, all enclosing the embryo, indicates that in the mature seed the embryo has attained a far-reaching physiological independence from its coat.
9 We have examined the aleuron grains in the embryo of H. marginata. ‘They include numerous globoids and one druse (cluster crystal) of calcium oxalate each. Treatment with picric acid and eosin also reveals a protein crystalloid (stained bright yellow) in the amorphous protein substrate (stained red). Thus they represent the most highly differentiated form of aleuron grains.
10Only the Subseries Seminudae has not been examined. The four species belonging to this group are considered to be hybrids and authentic seed could not be obtained.
11Jt seems unlikely because of basic differences in testa structure that EH. jacksoni and E. diversicolor are closely related. This is contrary to Blakely’s view since he places them in the same Subseries, Inclusae.
BY E. GAUBA AND L. D. PRYOR. 27
In some respects the testa as a whole may be compared with the (outer) bark. The suberized inner integument is a dead tissue and excretion of oxalate crystals and phlobaphenes into the outer integument excludes its cells from metabolic activities.
The series Steatoxylon and Myrtiformes, both of which Blakely places in his Renantherae-Normales, present a quite different type of testa.
E. microcorys, of the monotypic series Steatoxylon, has flat, bifacial somewhat elliptical seeds. The coat is much reduced in thickness. The inner integument is in the course of the ripening process resorbed and is missing altogether in the mature seed (PI. i, fig. 6). Only in the chalazal region, in the corner between the crystal layer and the inner cuticle, do a few non-suberized cells still appear. The outer epidermis is formed of thin-walled cells whose outer wall is often sunken (concave) or even torn and whose anticlinal somewhat wavy walis are partly separated from each other so that the seed surface appears somewhat shaggy. The inner epidermis forms a typical crystal layer in which each cell has a thickened basal wall and contains one large crystal enveloped in a cellulose membrane and some smaller ones. All cell walls of the integument give the tannin reaction with ferric salts. The major portion of the nucellus remnant is obliterated. Traces of endesperm are still seen, especially in the chalaza region, where, as with the nucellus remnant which also occurs there, cellular structure can be perceived. Here one can also see that suberized cells of the nucellus remnants contribute in a very high degree to the formation of the ‘chalaza cork: (Pl i} fiz. 5).
E. microcorys is distinguished therefore from the normal Renantherous type described above in the following ways:
1. The outer integument, except the raphe side, is only two-layered. The outer epidermis is composed of thin-walled cells which are often torn and separated from each other. The inner epidermis forms a typical crystal layer.
2. The inner integument is resorbed.
The other exception appears in the series Myrtiformes, of which Z£. deglupta, #H. brachyandra (Text-fig. 6 and Pl. i, fig. 9) and H. raveretiana were examined. The structure of the testa is in principle like that of H. microcorys except that the epidermal cells are of lesser depth, more elongated, with straight anticlinal walls, remaining attached to one another, and the outer wall is not torn. The inner periclinal walls of the crystal cells are only moderately thicker than the outer walls. The crystals are not enveloped in a cellulose membrane.
SECTION RENANTHERAE.
Blakely has erected a section Renantherae containing two series which are not in the section Renantherae-Normales, i.e. the Occidentaies and the Ochroxylon. Of the five species of the Occidentales we were able to examine H#. marginata, HE. staerii and H. sepulcralis, which agree with one another well and are characterized by the following features:
The outer epidermis has a cuticle-free, thick, strongly lignified outer wall which on the inside has a thick mucilaginous lamella extending along the side walls almost to the thin base wall of the cells (Pl. i, fig. 2). This mucilaginous layer is strongly impregnated with tannin material, swells in water displaying lamellations, and contracts in alcohol.”
The parenchyma of the outer integument is strongly developed and filled with tannin deposits. In EH. staerii crystals are scattered over the whole inner epidermis, while in #. marginata and E. sepulcralis they are confined to the hilar region.
The inner integument is suberized and in general two-layered, in H. staerii in some places three- or four-layered. The suberin lamellae display a fine granulation which
2 Staining to test the nature of this mucilage is masked by tannin impregnation. This can be removed by Eau de Javelle, whereupon chliorciodide of zine gives a dark blue colour and cuprammonia a light blue. This points to cellulose mucilage. On the other hand, ammoniacal ruthenium sesquichloride stains deep red, indicating the presence of pectin mucilage. It seems, therefore, that both kinds are present, if staining alone is a sufficient proof. There is no specific microchemical reagent for pectin.
28 SEED COAT ANATOMY AND TAXONOMY IN EUCALYPTUS. I,
was also observed in some of the Renantherae-Normales species, though to a lesser degree.
The nucellus remnant for the most part has lost cellular structure, but here and there it can be distinguished (PI. i, fig. 2).
This type of testa appears as a variant of the type of the Renantherae-Normales. The mucilaginous wall component of the epidermal cells does not represent a significant structural variation, since in an alcohol preparation the outline of the total thickening (cellulose plus mucilage layer) is exactly the same as that of the epidermal sclereids of the Renantherae-Normales. It is irrelevant to this study—and therefore has not been investigated—as to whether this mucilage as such has been deposited upon the cellulose walls or whether it is due to subsequent partial conversion of the walls into mucilage.
The structure of H. guilfoylei, of the monotypic series Ochroxylon, is quite different Cea, i, ile, 110). The outer integument of the flat seed is, viewed from the raphe-free side, formed from the two epidermal layers only. The cuticle-free outer epidermis is made up of thin-walled cells with walls impregnated with brown material which often adheres aiso to the wall in the form of irregular lumps which do not give any tannin reaction with FeCl;. The inner epidermis is a typical crystal epithelium. The inner integument is resorbed. The structure has therefore nothing in common with the large bulk of the Renantherae and resembles much more in general #. microcorys, with which it also has in common the cellulose envelopes of the crystals.
To sum up, we can therefore say that on the basis of testa structure the three series, Ochroxylon (#H. guilfoylei), Steatoxylon (H. microcorys) and Myrtiformes (£. deglupta, H. brachyandra and EH. raveretiana), do not conform to the combined group Renantherae and Renantherae-Normales. This evidence conforms with Maiden’s view of the relationship of HE. microcorys. He says (1, 262): “This species appears to stand by itself amongst the Renantherae to a greater extent than any other members of that group.” To place correctly HE. microcorys and the other species mentioned many more factors must be considered. This will be done at the conclusion of the anatomical study of the seed of the remainder of the genus.
There is also still another difference which separates these three series from the remainder of the Renantherae. This is the close placing of hilum and chalaza and consequently a different pattern of attachment of the seed and its vascularization.
The seed of the Renantherae is of somewhat irregular form, but it always displays about four or five raised ribs which spread out from a clearly marked basal hilum, that is at or near the base of the seed. As this type of seed originates from an anatropous ovule, the hilum lies in the vicinity of the micropyle through which the hypocotyl emerges. Therefore the germinating seed shows the hypocotyl close to the hilum at the base of the seed which is more or less perpendicularly attached to the ‘placenta, while the chalaza occupies the other end of the seed (Text-fig. 12). The vascular bundle diverging from the placenta as a single collateral strand into the outer integument ramifies sooner or later in numerous more or less arcuate ascending, not anastomosing, amphicribral branches which fan out over the chalaza, where they terminate (Text-fig. 19, 1). In transverse section they are seen arranged in a flat are facing the chalaza (PI. i, figs. 3, 4).
In the three series which do not conform to the general Renantherous pattern the seeds are bifacial with a ventral hilum, that is in the middle or perhaps a iittle towards the upper end of the one side, and close to the chalazal region, or even within it (as in #. microcorys).“ Thus the germinating seed shows the hypocotyl at the lower (micropylar) end and the hilum quite distant from it near the middle of the seed which is attached like a snield to the placenta (Text-fig. 13). This leads to
18 Discussing the ventral hilum of the Corymbosae, Maiden (VII, 95) mentions that after removal of the testa the scar beneath (this means probably on the inside) ‘is often larger and more distinct and definite in shape to that observed on the testa’. This “‘scar beneath” is of course the chalaza cork and has nothing to do with the scar of the hilum. The occurrence of hilum and chalaza face to face, or nearly so, is characteristic for seed with a ventral hilum, as in EH. microcorys.
BY E. GAUBA AND L. D. PRYOR. 29
the conclusion that such a seed originates from another type of ovule, the hemitropous. But further investigation must be undertaken when suitable material for ontogenetic study is available to see. whether this structure is not perhaps the result of change by growth of an ovule also originally anatropous. Goebel (1933) has illustrated by different examples a change by growth before or after fertilization resulting in an alteration of ovule shape, for example one originally anatropous becomes campylotropous (Geraniaceae) or an atropous ovule changes to hemitropous (TVorenia asiatica).
Through whatever phases these ovules may pass during their development the investigation of flower buds of H. microcorys just before anthesis shows that they are already of hemitropous shape (PI. i, fig. 7). The simultaneous occurrence of atropous ovules (Pl. i, fig. 8) will be discussed in connection with the chaff structure.
The phylogenetic and taxonomic importance of the ovule shape and structure has been emphasized often by many authors (see Warming, 1913), though in higher groups (families, ete.) different types may occur. In the Myrtaceae, for instance, the bitegmic anatropous ovule is dominant, but campylotropous ones occur too, and Jambosa caryophyllus is quoted as having only one integument. Thus it is not surprising that a genus as large as Hucalyptus has more than one ovule type.
Due to the ventral position of the hilum and in contrast with the elaborately ramified raphe bundle of the Renantherae, the conducting tissue of these three series is greatly reduced in extent and ramification, and its xylem built up by short, wide, irregularly shaped and sometimes branched tracheids with truncate ends, while in the Renantherae the tracheids are slender and long (Text-fig. 19, 1-6).
It is a well established fact that vessels in vegetative parts have undergone phylogenetic modifications culminating in the formation of short, wide vessel members with truncate ends (Bailey, 1944). Tracheids likewise have become shorter, though in a lesser degree. But too little is known about their structure and evolutionary trends in raphe bundles. Kuehn (1928) has investigated the course of intraseminal (= integumentary) bundles of the Angiosperms. Though this vascularization type does not occur in our species—there are only raphe bundles—her results are of great interest: the intraseminal vascular system has arisen independently in unrelated families, primitive and high ranking, and some families (Oleaceae, Leguminosae, Compositae, etc.) comprise genera with and without such bundles. This leads to the conclusion that they are of little phylogenetic significance. However, this does not mean that the vascularization pattern is of no taxonomic value for generic or infrageneric grouping.
Kuehn has not examined the Myrtaceae. Concerning the structure of intraseminal bundles she remarks only that they are built up by helically or annularly thickened tracheids. To our knowledge no other evidence in connection with taxonomic evaluation of seed vascularization has been published and its significance in the genus Hucalyptus will show up when all sections have been investigated. It already seems likely, however, that the two vascularization patterns are closely connected with the ovule type.
Finally. a few remarks on the nature and structure of the chaff seem appropriate.
We have examined these sterile bodies in H. muelleriana, E. laevopinea, H. alpina, #. obliqua, E. planchoniana, EH. oreades and E. fraxinoides. They are in principle in perfect confermity in all respects. The outer epidermis is similar to that of seed but encloses a tissue which may be best termed sclerotic parenchyma. On thin sections it has some resemblance to angular collenchyma in so far as the wall thickenings are apparently only in the cell corners while the side walls appear thin due to the very wide pits (Text-fig. 14). All cells are strongly lignified and filled with phlobaphenes staining inky black with ferric chloride. A disorganized vascular bundle can be located embedded in this tissue.
The chaff of HE. microcorys is of a strikingly different structure. While the seed epidermis is formed by thin-walled cells (Pl. i, fig. 5), the chaff epidermis is exactly of the Leguminosae type, that is to say, built up by palisade-like sclereids many times deeper than wide (Text-figs. 15, 16). The bodies forming this chaff are of very
I,
SEED COAT ANATOMY AND TAXONOMY IN EUCALYPTUS.
30
if).
Text-fig. 1: Eucalyptus dives;
3: E. brachyandra ;
qNiCcrocerys ; (ch, chalaza region; h, hilum. )
Bate
b) z
130x. 5: H. deglupta;
EH. gwilfoylei, tang. scalariform thickenings on the outer wa
raphe bundles, ca.
4: H. raveretiana;
1-6:
E. gwilfoylet.
67:
sect, of the outer epidermis o
Gr
f chaff with basal hilum showing
ca. 400x).
(photomicrograph,
ll
BY E. GAUBA AND L. D. PRYOR. 31
different size and shape, but they can be placed in two groups: small, narrow ones with a basal hilum, and larger, flat ones, often glossy, with a ventral hilum.
To trace their origin an ontogenetical investigation is needed. We could examine oniy flower buds just befere anthesis and this revealed the presence of two kinds of ovules in the ovary. Firstly, the fertile, at this stage already hemitropous ovules which have two distinct two-layered integuments with three cuticulae: an outer covering the surface, a median between the two integuments and an inner one delimiting the inner integument from the nucellus (Pl. i, fig. 7).1* These ovules develop after fertilization into seeds Icsing during maturation the outer and median cuticle and the inner integument.
Besides these fertile ovules there are many sterile, atropous ovules of prismatic shape, with basal hilum and distal micropyle. They are built up by a parenchymatous tissue with a procambial strand in the axis. At its apical end this parenchyma encloses a cavity leading into the micropyle and lined with a cuticle. The outline of this cavity varies with the section and is seen as either empty or containing a small, more or less isolated group of parenchyma cells (Pl. i, fig. 8). If we interpret this cuticle as the inner one, then the outer parenchyma represents a modified integumentary tissue and that within the cavity a modified nucellar tissue.
It is probably correct to assume that these sterile ovules mature finally into chaff with a basal hilum. Thus this chaff is already predetermined befcre anthesis. In conformity with the ovules from which it originates it shows a poor histological differentiation, the tissue consisting mainly of the epidermis and the parenchyma, both strongly sclerified and lignified (Text-fig. 16).
The chaff with a ventral hilum develops probably from fertile but not fertilized ovules. The hemitropous shape not only conforms with this suggestion, but also the richer tissue differentiation does too: outer epidermis, crystal layer, inner cuticle and an obliterated nucellus remnant, but of course no embryo (‘Text-fig. 15).
H. guilfoylei displays two similar kinds of chaff, of which we mention only the different architecture of their epidermal cells. All walls, except the inner periclinal ones, have conspicuous thickenings which are pitted even on the outer walls (blind pits) in chaff with a ventral hilum (Text-fig. 17), while in chaff with a basal hilum they are scalariform or scalariform-reticulate (Text-fig. 19, 7). As mentioned earlier, the seed epidermis of this species is thin walled (Text-fig. 10).
Thus, not only the seed coat but the chaff structure too deserves consideration and may contribute valuable information for taxonomic problems.
References.
Baitpy, I. W., 1944.—The Development of Vessels in Angiosperms and its Significance in Morphological Research. Amer. Jour. Bot., 31: 421-428.
BENTHAM, G., 1866.—Flora Australiensis, Vol. 3.
BLAKE, S. T., 1953.—Botanical Contributions of the Northern Australia Regional Survey, I, Studies on Northern Australian Species of Eucalyptus. Aust. Jowrn. Bot., I, No. 2: 185-352.
BLAKELY, W. F., 1955.—A Key to the Eucalypts (2nd edition).
GOEBEL, K., 1933.—Organographie der Pflanzen, 3 (3rd edition).
HarapA, M., 1956.—Anatomical Characteristics of the Seed Integument observed on 10 species of Eucalyptus. Reports of the Kyushu University Forests, No. 6: 1-14.
KUHN, G., 1928.—Beitrage zur Kenntnis der intraseminalen Leitbiindel bei den Angiospermen. Bot. Jahrb., 61: 325-379.
MAIDEN. J. H., 1929.—A Critical Revision cf the tfenus Hucalyptus, 7.
MULLER, F. v., 1879-1884.—EHucalyptographia.
NETOLITZKY, F., 1926.—Anatomie der Angiospermen Samen. In: K. Linsbauer, Handbuch der Pflanzenanatomie, 10: 14.
Petit, L. A., 1908.—Recherches sur la Structure anatomiaue du Fruit et de la Graine des Myrtacées (Dissertation, Paris).
Pryor, L. D., 1956.—An Fil Hybrid between Hucalyptus pulverulenta and EH. caesia. Proc. Linn. Soc. N.S.W., 81, Part 2: 97-100.
WARMING, H., 1913.—Observations sur la Valeur systématique de lOvule. Mindeskrift for J. Steenstrup (Copenhagen).
147The outer cuticle is a single membrane, the two others are of double nature, as can be seen where the two integumelts ‘separate from each other (Pl. i, fig. 7) or the nucellus Separates from the testa (Pl. i, fig. 8).
32 SEED COAT ANATOMY AND TAXONOMY IN EUCALYPTUS. I.
BXPLANATION OF PLATH I. Cork tissue and cuticles brown.
1: Hucalyptus laevopinea, part of transy. sect. of seed. 2: H. marginata, part of tranv. sect. of seed. The mucilage layers of the epidermis (mu) swollen by water absorption. Nucellus (7) partly crushed. 3: EH. tasmanica, part of transv. sect. through the raphe-chalaza region at the level of the cuticula gap (the inner cuticle, ic, ending blind in the chalaza cork). 4: H. stellulata, part of tranv. sect. through the raphe-chalaza region, somewhat below the cuticula gap (the inner cuticle, ic, is running through). The tracheids (t) of the amphicribral raphe bundle fan out over the suberized chalaza (che). 5: H. microcorys, longit.-radial sect. through the raphe-chalaza region and the cuticula gap showing the course of the raphe bundle (rb) and the gap in the crystal layer (cr) and inner cuticle (ic). 6: H. microcorys, part of transy. sect. of seed. 7: EH. microcorys, diagram and micropyle of the hemitropous ovule showing the three cuticulae (oc, mec, ic). 8: H. microcorys, leng. sect. of a sterile atropous ovule with the single outer and the double inner cuticle. 9: H. brachyandra, part of tranmsy. sect. of seed. 10: H. guilfoylei, part of transy. sect. of seed. All figures (except the diagram) ca. 180x. Figs. 7 and 8 microtome sections.
ch, chalaza ; che, chalaza cork; cr, crystal layer; e, embryo; ec, embryo cuticle; en, endosperm; ic, inner cuticle; ie, inner epidermis; ‘w#, inner integument; mc, median euticle; mu, mucilage; n, nucellus; nr, nucellus remnant; oc, outer cuticle; oe, outer epidermis ; oi, outer integument; pl, placenta; ps, procambial strand; rb, raphe bundle; ¢t, tracheids.
33
A NEW SPECIES OF AEDES (FINLAYA) FROM NORTHERN AUSTRALIA (DIPTERA, CULICIDAE).
By EvizagetH N. Marxs, National Mosquito Control Committee, Department of Entomology, University of Queensland, and Ernest P. Hopexin, Department of Zoology, University of Western Australia.
(One Text-figure.)
[Read 26th March, 1958.]
Synopsis. Both sexes, larva and pupa of Aédes (Finlaya) Obritteni, n. sp., are described from northern Western Australia. It occurs also in Northern Territory. The affinities of A. britteni are discussed and it is placed in a new subgroup of Group D of the subgenus Finlaya.
For many years only two species of the subgenus Finlaya, Aédes notoscriptus (Skuse) and Aédes purpureus (Theobald), were known from northern Western Australia. Hodgkin and Britten (1955) recorded a third, undescribed, species which is here described as Aédes britteni, n. sp. It has since been found also in Northern Territory by Mr. A. K. O’Gower, to whom we are indebted for the opportunity to study his specimens.
AEDES (FINLAYA) BRITTENT, N. Sp.
Distinctive Characters.
Adult: This is the only Australian Finlaya with hind tarsal segment V white with a narrow basal dark band; other distinguishing characters are dark-scaled proboscis and wings; absence of scutal pattern; scutellar scales ali broad, white; small patches of broad white scales on pleuron, including paratergite; hind tarsal segment IV all dark. ’
Larva: Antenna long, swollen near base; head setae 5 and 6 single or bifurcate, 14 short, stout, single; lateral comb a single row of fringed scales; distal margin of saddle without spines.
Description of Adult. a
Female—wWing length 3:8 mm. Head: Integument orange-brown, clothed mesially with rather sparse narrow-curved creamy scales, in front of which is a continuous band of narrow-curved black scales, terminating laterally in a small patch of fiat black scales, below which are flat creamy scales. There is a wide ocular border of flat silvery-white scales, discontinuous at vertex, but a few narrow silvery scales extend between the eyes. Upright forked scales long, black, numerous. A pair of strong black vertical bristles with two pairs of smaller bristles above them and a row of five strong mesially-directed ocular bristles, with finer bristles laterally. Torus dark brown with some small dark setae mesially; flagellar segments of antenna black with short silvery clothing hairs and sparse black verticillate hairs; first flagellar segment paler on basal half and with flat black scales mesially. Clypeus dark brown. Palps and proboscis black scaled; palp 0:2 length of proboscis, which is 1:2 length of fore femur. lLabella dark brown.
Thorax: Integument bright orange-brown darkened beneath the silver scale patches. Scutum clothed with rather sparse fine narrow-curved dark brown scales. Bristles strong, black, about 13-16 acrostichal, 12-14 dorsocentral, 9-10 prescutellar, a group above wing roots, scattered bristles along lateral margin of scutum, and one on fossa. Scutellum darker brown, all lobes densely clothed with broad flat silvery-white scales; 4-6 long black bristles to each lobe in addition to shorter bristles.
-PROCEEDINGS OF THE LINNEAN SocineTY OF NEW SOUTH WALES, 1958, Vol. Ixxxiii, Part 1.
34 A NEW SPECIES OF AEDES (FINLAYA) FROM NORTHERN AUSTRALIA,
There is a patch of broad silvery-white scales on apn, propleuron and paratergite, a small patch on posterior margin of ppn below the bristles, on upper stp, on lower posterior margin of stp, and on upper msp. Bristles black; apn with 3-4 very strong bristles above, numerous others below; 5 long and 1-2 shorter propleural; 4-5 strong ppn; 3-4 postspiracular, one upper stp and 2-3 long bristles along posterior margin of stp in addition to finer bristles; 8-9 prealar; 8-10 lighter brown upper and no lower msp bristles.
Legs: Black scaled with purplish-blue reflections and banded tarsi. Coxae and trochanters yellowish-brown; fore coxa with mixed dark and pale scales, mid and hind with patches of silvery scales, hind also with some dark scales below; trochanters dark scaled, mid and hind with pale scales posteriorly. Fore femur with pale scales dorsally on basal 1/4, and extending as a tapering streak posteriorly for 2/3-3/4 length and with a small silvery-white kneespot; tibia dark except for a few white scales dorsally at base; tarsal segments I and II with basal white bands covering 1/5-1/4 I and 1/3 II, I also with a small white apical dorsal patch, and one or two white scales at apex of II and a few scales or small patch at base of III. Mid-femur with creamy scales showing anteriorly as a small basal patch, extending on basal 1/4-1/3 dorsally and as a tapering stripe on basal 1/2-3/5 posteriorly, and with white kneespot; tibia as on fore leg; tarsal segments I and II with basal white bands covering 1/5-1/4 I, 1/3 II, basal patch 1/5-1/3 III, and a few pale scales also at apex of I, II and V. Hind femur with white kneespot and with small dorsal basal patch of creamy scales which has a few pale scales below it anteriorly, and extends as a tapering streak on basal 1/3 posteriorly. Tibia entirely dark or with a few white scales at hbase; tarsal segments I-III with basal white bands covering 1/5 I, 1/4-1/3 II and 1/3 III, I and II also with small patches of white scales apically, IV all dark, V with basal 1/5 dark, and a ventral line of darkish scales, remainder white. Claws equal, those of fore and mid legs toothed, hind simple.
Wings: Black scaled, outstanding scales all long and narrow. Cell R2 1:5-1:6 times length of its stem; cell M1 0:8 times length of its stem, its base slightly proximal to that of cell R2; r-m twice its own length distal to base of M3+4. Halteres pale with dark scales on knob and a few dark and pale scales on upper side of stem.
Abdomen: Mainly black scaled with purplish-blue reflections; ‘numerous black bristles along apical and lateral margins of tergites II-VIII and scattered over tergite I and the sternites. Tergite I dark scaled mesially, with silvery-white scaled lateral margin; tergite II with a pair of submedian basal patches of pale-refilecting scales, contiguous with large lateral basal patches of silvery-white scales; III-VI with a broad basal patch of pale scales, covering 1/2—2/3 length of tergite, indented in mid-line on III-V, and with small patches of silvery-white scales slightly removed from basal and lateral margins; VII dark with large lateral white patches, VIII short, dark scaled. Sternites dark scaled, VIII large, exserted, integument dark basally, yellowish-brown apically, clothed with fine hairs and bristles, bare of scales. Cerci short, dark.
Described from the holotype and one paratype female. The holotype has the scutum and scutellum slightly rubbed.
Four females from Roper River Mission show the fcllowing differences from the foregoing description: Wing length 3:6-4:-7 mm. Some small dark scales mesially on torus (possibly obscured by shrinkage in holotype and paratype); 18-25 acrostichal, 11-13 prescutellar bristles; 7-8 long bristles on lateral lobe of scutellum; 2-4 ppn, 1-5 postspiracular, 1-2 upper sty and 7-16 prealar bristles. Fore leg: Basal band 1/4-1/3 tarsal segment II; there may be no pale scales at apex of I and II or base of III. Mid leg: Pale scaling at base of femur may be reduced dorsally; basal band 1/4-1/3 tarsal segment II; there may be no pale scales at apex of I, II and V. Hind leg: Posterior stripe may extend to mid length of femur; basal white bands 1/5-1/4 tarsal segment II, 1/4 III; basal 1/4 V dark; no pale scales at apex of I and II. Wings: Cell R2 1:4-2:0 times length of its stem; cell M1 0-7-1:0 times length of its stem, their bases may be level; r-m 2-8 times its own length distal to base of M3+4. Abdomen: Median patches of abdominal tergites may be indented on III—VI or lack indentatio on IV-VI. :
BY ELIZABETH N. MARKS AND E. P. HODGKIN. 35
Male.—Resembles the female except as follows: Wing length 2:9-3:-2 mm. Head: White scales between the eyes may be broad; lateral patch of flat black scales may be absent. Torus large, dark, with fine short setae on mesial aspect; flagellar segments of antenna brown with dense dark verticillate hairs lying mainly in an almost vertical plane, first segment with some flat dark scales distally; two apical segments elongate, dark, with silvery clothing hairs. Palps about equal in length to proboscis, dark scaled with a small white basal band on segment III, sometimes also on II, and wide white basal bands covering 1/5-1/4 IV and 1/2 V; segments IV and V down turned, without dense hairs but with short dark bristles, about 6 at apex of III, 6 or 7 at apex of IV and 4-6 at tip of V, as well as 12-18 along lower side of IV and numerous finer bristles along V.
Thorax: 10-13 acrostichal, 9-16 dorsocentral, 4-9 prescutellar bristles. On mid lobe of scutellum the white scales may be divided inte two patches by a narrow median unscaled line; apn with 2-3 strong bristles above; 5-7 upper msp bristles.
Legs: Mid coxa may have a few dark scales below; hind coxa may have white scales only; fore trochanter may be pale scaled posteriorly. Fore leg: The pale posterior streak on femur may extend almost to apex; tibia may be dark basally; basal bands covering 1/5-1/3 tarsal segment I, 1/4-2/5 II. Mid leg: Femur with a streak on basal 1/3—2/3 posteriorly; tibia may be dark basally; basal bands covering 1/5-1/3 tarsal segment I, 1/4-1/2 II, III sometimes and V usually all dark. Hind leg: Femur may have a complete ring of pale scales at base, or be dark to base anteriorly with streak on basal 1/4-1/3 posteriorly; basal white bands covering 1/5-1/4 tarsal segment J, 1/5-1/3 III. On fore and mid legs, tarsal segment IV is 1/2 length of V; claws (Fig. 1, a, 0) large, unequal, pilose basally, the anterior long with a strong blunt tooth near mid length and usually with a slender pointed tooth arising laterally at base (the strong tooth reduced on one mid claw in one specimen), posterior claw shorter, with pointed subbasal tooth. Hind claws equal, simple.
Wings: Cell R2 1-2-1:5 times length of its stem, cell M1 0-6—0-8 times length of its stem. Halteres with dark scales on knob and running down dorsal side of stem, sometimes with a few pale scales on knob and stem.
Abdomen: Tergite II may have a pair of small submedian basal patches of pale- reflecting scales, III-VI with median basal paie patches 1/4-3/4 length of III and IV, 1/3-3/4 length of V and VI, indented in mid-line on III and frequently also on IV-VI; VII dark mesially or with median basal pale patch 1/3 its length; true tergite VIII dark scaled or with a few silvery scales laterally. Sternites dark scaled, IIJ-VII may have silvery lateral patches at mid length, VII may also have a median basal patch; VIII with large median basal patch of silvery scales.
6 Terminalia (Fig. 1, c): Coxite densely clothed with setae and with large patches of silvery scales laterally at base and dark scales towards apex; cylindrical, about four times as long as broad at base, with a membranous area along its inner aspect. The slightly developed basal lobe bears a dense patch of about 60 medium length setae, those in the outer row appearing somewhat stouter; extending distally from this patch, along the tergal side of the membranous area are about six rows of short fine setae, which become longer near apex of coxite. Extending along the sternal side of the membranous area on distal half of coxite are three rows of medium length fine straight setae; sternal to these again, running the length of the coxite and likewise directed mesially are 3-4 rows of longer stouter finely striated setae, the more distal of which are the longest. There are numerous scattered long setae on the sternal, lateral and outer tergal aspects of coxite, densest towards apex; there are also a few shorter setae sternally at base. Style 2/5 length of coxite, strongly curved, slightly tapering, non-pilose, with 1—2 short preapical setae; terminal appendage 1/7-1/6 length of style, stout, apparently grooved with rounded tip. Harpago about 1/3 length of coxite, stout basally, more slender on apical half, pilose except near apex, with a row of 7-9 slender setae mesially on basal half; just beyond these tergally arise two longer setae, reaching to apex of harpago; appendage about 4/5 length of harpago, broadening on basal third, then tapering to a slender pointed tip, fairly evenly sclerotized except for membranous broadening near base. Paraproct with single tooth. Phallosome simple,
36 A NEW SPECIES OF AEDES (TINLAYA) FROM NORTHERN AUSTRALIA,
elongate, tapering distally. Lobes of IXth tergite with 6-10 stout setae; IXth sternite with 15-16 short setae. :
Larva (Fig. 1, d-k)—Nomenclature of setae as in Belkin (1950). Length about 8-10 mm. Cuticle dark. Setae in general rather short.
h ee
7 ; m
Fig. 1—Aédes britteni, n. sp. a-c. Male: a. Anterior and b. posterior claw of foreleg. ec. Terminalia (tergal view; blade of left harpago omitted).
d-k. Larva: d. Head. e. Prothoracic setae 1-3. f. Base of mesopleural and g. base of metapleural setae (ventral view). h. Terminal segments. i. Lateral comb tooth. j and k. Pecten teeth, 7 from apex and k from middle of pecten.
l-m. Pupa: Jl. Cephalothorax (head capsule separated). m. Metathorax and abdomen (dorsal setae on left, ventral on right).
BY ELIZABETH N. MARKS AND E. P. HODGKIN. 37
Head: 0-8-0:9 times as long as broad. Antennae 0-6—-0-8 length of head, slightly curved, broadening just above base (greatest breadth is 0:14-0:18 length of antenna), then tapering to terminal. third which is parallel-sided; with sparse fine spicules; seta 1 arising at about mid-length, stout, plumose, single or bifurcate near tip, 0:3-0:5 length of antenna; terminal and subterminal setae arising close together, 2 moderately long, 3 short, 4 shorter than 2, 5 broad with pointed tip, 6 short. Head seta 1 single, slender, curved, simple; base of 7 slightly behind base of antenna, 6 level with base of antenna and about 0-6 distance from 7 to midline, 5 slightly posterior to 7 and lateral to 6, 4 mesial to and about midway between 5 and 6; 4 short, fine, 7-15-branched; 5 and 6 about 0-5-0-6 length of antenna, stout, plumose, single or rarely bifurcate beyond mid-length; 7 plumose, 6—10-branched; 8 long, single; 9 3—-6-branched; 10 2-6- branched, rarely single; 11 5-10-branched, plumose; 12 single to trifid; 13 fine, 5-10- branched; 14 short, stout, single; 15 short, single. Setae of mouthbrushes apparently all simple in 15 specimens; some of the more mesial setae finely pectinate in seven specimens, including skin of holotype. (The occurrence of this type of dimorphism in some species was first brought to our attention by Mr. P. F. Mattingly.) Mentum triangular with median pointed teoth and 9-12 pointed lateral teeth, of fairly even length, but the more lateral ones stouter.
Thorax: Prothoracic setae 1, 2 and 3 without sclerotized bases, 1 the longest, single or rarely bifid, finely plumose; 2 single, simple, about 0:6 length of 1; 3 fine, 5-10- branched, about ‘0:2 length of 1; 14 short, single or bifid. The bases of the meso- and metathoracic pleural setae bear very large curved pointed spines.
Abdomen: Seta 6 on segments I-VI in length about 0:5 width of segment; on I and II 2—5-branched, stout, plumose, arising from a large sclerotized base; on III-VI bifid (rarely trifid on III), slender, finely frayed. Seta 7 on I slightly shorter and finer than 6, 2-3-branched, piumose, arising from same base as 6; on II about 0-5 length of 6, 2-8-branched, plumose, arising from a separate sclerotized base. Highth segment: Lateral comb a single curved row of 13-20 broad, apically rounded, coarsely fringed scales (in one specimen one scale was posterior to the row; in one specimen, one comb tooth was a small spine); seta 1 2-4-branched, finely frayed; setae 2 and 4 single, simple; seta 3 5-9-branched, plumose, arising from a small sclerotized base; seta 5 2—4-branched, frayed. Siphon slightly tapering, with small acus; index 2-2-2-9; pecten extending over basal 0:-4-0-5 of siphon, of 15-23 close-set dark spines with 2-4 fairly even-sized denticles near base; the spines gradually increase in size from the base of the siphon, the distal ones very long, with inconspicuous denticles; seta 1 arising at 0-6-0:7 length of siphon, 2-3-branched, finely frayed, about 0-3 length of siphon; seta 8 single to trifid. Anal segment: Saddle covering about dorsal 0-9 of segment, without apical spines; seta 1 single, simple, about 0:6 length of saddle; seta 2 11-20- branched, about equal in length to saddle; seta 3 single, about 2:5 times length of 2; seta 4 of 11 14-22-branched tufts arising from a grid and 1 smaller precratal tuft; anal papillae pointed, subequal, the lower 0:7 or more length of upper which are almost equal in length to saddle.
Described from four skins, correlated with the holotype, allotype and two paratype males, and 18 morphotype larvae.
Pupa (Fig. 1, 1, m)—The nomenclature of the setae follows Belkin (1952, 1958). The setae are simple, unless stated; their lengths are indicated in the figure.
Cephalothorax: Trumpet evenly pigmented, 2-7-3-2 times as long as greatest width, with oblique opening; ratio of meatus to whole 1 : 1-5-1:7, apical notch shallow. Setae 1, 2 and 3 single; seta 4 single to trifid; seta 5 single; setae 6 and 7 2~3-branched; seta 8 2-5-branched; seta 9 single; seta 10 single or bifid; seta 11 single; seta 12 single to trifid.
Abdomen: Segment I. Seta 1 strongly developed, with about 10 primary branches each subdividing into 2—4 simple or sparsely plumose branches. Seta 2 single or bifid; seta 3 single, may be inconspicuously frayed; seta 4 single or bifid; seta 5 2—3-branched; seta 6 single to trifid; setae 7 and 10 single. Segment II. Seta 1 single to trifid, may be inconspicuously frayed; setae 2 and 3 single; seta 4 2-4-branched; seta 5 3-5- branched; seta 6 single or bifid; seta 7 single; seta 10 single or bifid, Segment III.
Cc
38 A NEW SPECIES OF AEDES (FINLAYA) FROM NORTHERN AUSTRALIA,
Seta 1 single to trifid; setae 2 and 3 single; seta 4 single or bifid; seta 5 3—4-branched; seta 6 single to tetrafid; seta 7 single; seta 8 2-3-branched; seta 10 single to trifid; setae 11 and 12 single. Segment IV. Seta 1 single to trifid; setae 2, 4 and 5 single; setae 3 and 6 single to tetrafid; seta 7 single; seta 8 single or bifid; seta 10 2—3-branched; seta 11 single; seta 12 single or bifid. Segment V. Setae 1 and 3 single or bifid; seta 2 single; seta 4 2-5-branched; seta 5 single; seta 6 single to pentafid; seta 7 single; seta 8 single or bifid; seta 10 2-3-branched; setae 11 and 12 single. Segment VI. Setae 1, 2, 3 and 5 single; setae 4 and 6 single or bifid; seta 7 single; seta 8 2—4-branched; setae 10, 11 and 12 single. Segment VII. Setae 1, 3 and 5 single . or bifid; setae 2 and 4 single; seta 6 4-5-branched; seta 7 stout, single; seta 8 single to trifid; setae 10, 11 and 12 single. Segment VIII. Seta 5 single; seta 7 stout, single, slightly frayed. Paddles broad with bluntly pointed apex; index 1:2-1:5; midrib moderately and buttress slightiy developed; fine denticles along margin; seta 1 single.
Described from three pupal skins, one correlated with the allotype and two with paratype males.
Types: Holotype female, Kalumburu (Drysdale River Mission), 14° 25’ §., 126° 37’ H., Western Australia, 14.111. 1954 (0830-7), EH. P. Hodgkin. Allotype male (0830-9), one paratype female (0830-8), four paratype males (0830-5, -6, —10, —11), and 18 morphotype larvae, same data as holotype. The holotype has a correlated larval skin, and the allotype and two paratypes (0830-5, -10) have correlated larval and pupal skins.
Holotype, allotype, one paratype male and six morphotype larvae in University of Queensland collection; paratype male’ (with correlated skins) and female and six morphotype larvae in University of Western Australia collection; one paratype male and two morphotype larvae in C.S.I.R.O. Division of Entomology collection, Canberra; one paratype male (with correlated skins) and two morphotype larvae in British Museum (Natural History); two morphotype larvae in School of Public Health and Tropical Medicine, Sydney.
This species is named after Mr. H. J. Britten, of the Department of Public Health, Western Australia, whose collections have added considerably to knowledge of mosquitoes of that State. ;
Biology: The type series was bred from larvae collected from a rot hole in the fork of a baobab tree (Adansonia gregortui). Hodgkin and Britten (1955) noted that larvae of A. purpureus which were found in the same treehole were preying on the larvae of A. britteni. The mean annual rainfall at Kalumburu is 37 inches, almost all of it falling from November to April. Mr. O’Gower found adult females occurred not infrequently in collections at the Roper River Mission, where the mean annual rainfall of 28 inches has a similar seasonal distribution.
Distribution: WESTERN AUSTRALIA: Kalumburu (the type series). NORTHERN TERRI- TORY: Roper River Mission, 14° 8’ S., 134° 8’ H. (17, 21, 22, 23.iv.1957, A. K. O’Gower).
Discussion: Though it lacks the characteristic pattern of lines on the scutum, A. britteni belongs to Group D (aureostriatus-group) of the subgenus Finlaya, in which Knight and Marks (1952) recognized eight subgroups.
It shows relationships to A. quasirubithorua (Theobald) and A. keefei King and Hoogstraal (subgroup IV, quasirubithorax) and also to A. candidoscutellwum Marks (subgroup V, candidoscutellum), species which occur in north-eastern Australia and New Guinea. Males of both subgroups IV and V differ from A. britteni in having long hairs on the distal segments of the palp instead of short bristles.
A. britteni resembles A. candidoscutellum (which sometimes lacks a scutal pattern) in having broad white scales on the scutellum and in small patches on the pleuron, but in A. candidoscutellum the paratergite is bare (usually ppn also). The male terminalia of A. britteni bear a fairly close resemblance to those of species in sub- group IV, but differ in the short stout appendage of the style and the long setae on the harpago; the resemblance is less close to A. candidoscuiellum which, however, has long setae on the harpago. The larva of A. britteni resembles those of both subgroups in the shape of the head, the long antennae, the form and position of head setae 5 and 6. The shape of the antennae and the form of seta 14 in A. britteni are distinctive. The
BY ELIZABETH N. MARKS AND E. P. HODGKIN. 39
lateral comb is similar in A. britteni, A. quasirubithoraxy and A. keefei, but the two latter species have distinct fine spines on the distal margin of the saddle.
The foregoing differences indicate that A. britteni does not belong to either sub- group IV or V; nor does it fall into any of the other six subgroups of Group D. Another species from eastern Australia, A. wasselli Marks, which belongs to Group D and is known from females only, could not be placed in a subgroup by Knight and Marks (1952). A. wasselli has a scutal pattern and subspiracular scale patch; other- wise the thoracic scaling quite closely resembles A. britteni and the two species appear likely to be nearly related. The following definition (in the terms of Knight and Marks, 1952) of a new subgroup to include A. britteni has therefore been widened to allow the tentative inclusion of A. wasselli also.
Group D (aureostriatus-group: Hulecoeteomyia). Subgroup IX, britteni. Defini- tion: Australasian. Male palpi with segments IV and V downturned, III-V with a few strong apical hairs; short hairs only along IV and V (male of wasselli unknown). Basistyle without a specialized scale tuft. Hind tarsi with basal pale bands on I-III, I and II with or without apical pale patches or bands; V all white or with basal dark band. No postspiracular scales. Paratergite scaled. Subspiracular scales present or absent. Supplementary characters: Claspette filament blade-like. Female tori with fine hairs medially. Scutal linear pattern distinct or wanting. No prealar scale patch. Larval head hair 5 posterior to 6, 7 and 4 on a line between 5 and 6. Comb consisting of a curving row of scales. Larval habitat: treeholes. (Larva of wasselli unknown.)
References. BELKIN, J. N., 1950.—A revised nomenclature for the chaetotaxy of the mosquito larva (Diptera: Culicidae). Amer. Midl. Nat., 44: 678-698. , 1952.—The homology of the chaetotaxy cof immature mosquitoes and a revised nomenclature for the chaetotaxy of the pupa (Diptera, Culicidae). Proc. ent. Soc. Wash,, 54: 115-130. , 1953.—Corrected interpretations of some elements of the abdominal chaetotaxy of the mosquito larva with pupa (Diptera, Culicidae). Proc. ent. Soe. Wash., 55: 318-324. HopGkKIn, EH. P., and Britten, H. J., 1955.—A survey of the mosquito fauna of tropical Western Australia. Rep. Comm. publ. Hlth. W. Awst., 1953: 97-107. KnicHT, K. L., and Marks, EH. N., 1952.—An annotated checklist of the mosquitoes of the subgenus Finlaya, genus Aédes. Proc. U.S. nat. Mis., 101: 513-574.
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40
A SUMMARY OF THE ATOPOMELINAE (ACARINA, LISTROPHORIDABE). By Rogsrert Domrow, Queensland Institute of Medical Research, Brisbane. (Nine Text-figures.)
[Read 30th April, 1958.]
Synopsis.
The known species of atopomeline fur-mites are listed, and keys are given to the genera and to the species of the large and essentially African genus Listrophoroides.
Two new Australian species are described: Awstrochirus perkinsi, n. sp., from the koala (Phascolarctos) and Atellana papilio, n. g., n. sp., from the brush-tailed possum (Trichosurus).
Cumpylochirus is shown to contain only the geno.ype, C. chelopus, from Pseudocheirus in Tasmenia.
Neolabidocarpus, from Macropus in New Guinea, of which only the holotype nymph appeais . be ex.ant, has been reexamined and shown to be an atopomeline and not a labidocarpine genus. Its exact status remains uncertain. F
New combinations: Listrophoroides adherens (Trouessart, 1893) and Chirodiscoides oryzomys (Radford, 1954).
New synonymy: Marquesania Wornersley, 1943 = Listrophoroides Hirst, 1923; Listro- phoroides trdgdrdhi Radtord, 1940 = Marquesania expansa form queenslandica Womersley, 1943 = Listrophoroides expansus Ferris, 1932; Marquesania elongata Lawrence, 1951 = Listro- phoroides mastomys Radford, 1940; Marquesania imbricata Lawrence, 1954 = Listrophoroides lemniscomys Radford, 1940; Cricetomysia andréi Lawrence, 1956 = Campylochirus cheloprs Trouessart, 1893.
A study of the atopomeline fur-mites which have accumulated recently at this Institute has yielded two new species and given supplementary data on certain other Australasian species. This led to an interest in the essentially African genus Listrophoroides, and the subsequent receipt of an extensive collection of this genus from Dr. C. D. Radford induced me te add a synopsis of the known genera and species of the subfamily. Twelve genera and 35 species have been included in this group, of which 10 and 29 respectively are here recognized. | Species not commented on in the text are readily recognizable from the available descriptions.
This paper is not meant to be a full study of the subfamily, but simply to elucidate the known genera and species, many of which have long been unrecognizable. It is certain that new genera and species remain to be found, and the following generic key is not designed to indicate relationships. For example, I suspect that Tenrecobia will prove quite close to Listrophoroides.
Key to genera of Atopomelinae.
1. Clasping apparatus enlarged posteriorly, forming a pair of clam-like flaps between coxae II and III. Female with anterior half of body covered dorsally with two shields and posterior half covered by small, pointed papillae. Males with legs IV grossly enlarged, extending far beyond end of abdomen, and as long as entire body; basal movable SERGE SrA, WR) SUOMI SITHAGES oot anoscoosmooanDestnDUodesOu OS onesas Atopomelus.
Clasping apparatus not so enlarged posteriorly. Body of female, if covered with papillae, with single dorsal shield (Austrochirus). Leg IV of male moderately enlarged, and, even if reaching beyond end of abdomen, never more than half as long as body;
. Wal uowKe, Shoo Om lose “maenwelolkey GesMAeMe goconorevonsbenuouopeaudsunobosoUSmSaO rae
2. Posteapitular shield with narrow transverse frental lobe arched over the capitulum,
producing a hunched facies; clasping apparatus immediately followed by a transverse
band sOftStOURCEetrOLSE SDINESE leeNere eet emer ee erence tein ne dace trot nec eh er ak oo ae Atellana. Postcapitular shield simple, and set behind the evenly tapering capitulum; no spines behind AclaSpinig "App AACS eye lepers asic wusioawe tepleemedeye xowtausliomeyroiiel s\ sieve! tobe vos 2) stiees ca ieiccd cure OReRe RoR 3.
3. With transverse oval shield immediately behind longitudinal postcapitular shield ........ st ae oa) oa Gee tt ne S1G CO LL OICHOROED DVOTOIOTO OCOD Clo CIOS 8 crow cia bo orcnoteDra ete Tenrecobia.
PROCEEDINGS OF THE LINNEAN SOCIETY OF NEw SoutTim WALES, 1958, Vol. Ixxxiii, Part 1.
BY ROBERT DOMROW. 41
4, Postdorsal shield not separated from middorsal shield ....................----se0.> 5. Postdorsal shield (if present) widely separated from mid- or anterodorsal shield ..... CG
5. Abdomen of female with long, thin process arching forward over dorsum; leg IV of male much’ enlarged and modified, including tarsus .........2..5...---.4-<«.. Campylochirus. Abdomen of female without long terminal process; leg IV of male only slightly enlarged and with normal tarsus ....... Peery eae ete Sate caverta Rent all SAE ROR CMT Col sree oteg SgeLsau sph oh a ssiier Susie) whanerse 6.
6. Postdorsal shield of female covering entire hysterosoma (except extreme apex). Male with tarsus IV straight, bearing caruncle apically, and without anal suckers ........ EE at ed scare R Seo eST sek seat visto ey a ovleabe: Ausmevarobaus iat ech oMamohegey elisterainavecate Alters Listrophoroides.
Postdorsal shield of female truncate, occupying only anterior half of hysterosoma. Male with tarsus IV hooked, bearing caruncle subdapically, and with large anal suckers PR MoM a saci taster syiayr sitar su ahsbises fattayediei riot aige erg cs snicriamteistysu etnies vsecet er eh aneuey eye eavnaticl a engeauen's! wate . Chirodiscoides. With two broad anterior dorsal shields, the hinder one deeply concave anteriorly to accept convex posterior margin of the other; third dorsal shield separated from middorsal SIAN! lonir loueOeVel loguovel Ore Biavonsillengeol pil osonuooacoccogeon0ddudooaudHdD Cytostethum. With only single dorsal shield anteriorly (which may have lateral accessory lobes) ; male sometimes with a postdorsal shield, which is widely separated from anterodorsal
=
STC ret cBopeticnes cates tex cliccay steuciomepematee el osislian sicohistis heya lietiet «! aribs etiyeicettenia aliguaties myer entaera: es: c6l s}iale/ aucyeite yee ve wih venire 8.
8. With compact, well developed striate clasping apparatus between coxae I and II. Male HEM, [Une Ore loslavioel Coxe INS aooococoodcocvguedsoucesecuespobue Austrochirus. Described as having coxae I and II widely separated medially, and lacking a striate clasping apparatus; male genitalia between coxae III .................... Centetesia.
AUSTROCHIRUS Womersley. AUSTROCHIRUS QUEENSLANDICUS Womersley, 1943 (genotype).
The type series of this species is recorded and labelled as from the phalangerid Trichosurus vulpecula (Kerr), and I had considered the two unnamed species from this host and from bandicoots listed in the Annual Report on the Health and Medical Services of the State of Queensland for the year 1937-38 to be the same. Subsequent collections, however, have shown that A. queenslandicus occurs only on the bandicoots Thylacis obesulus (Shaw and Nodder) and Perameles nasuta Geoffroy, and have yielded a new genus and species described below from Tvrichosurus. It seems certain that mislabelling has occurred, and that the type host of A. queenslandicus should be T. obesulus, not the phalangerid.
AUSTROCHIRUS ENOPLUS Domrow, 1956. The holotype female and allotype male of this species are now in the Queensland Museum, Brisbane.
AUSTROCHIRUS PERKINSI, 0. Sp.
Types: Holotype female and allotype male in Queensland Museum, Brisbane; paratypes of both sexes in U.S.N.M. and B.M. (N.H.). All specimens from the koala, Phascolarctos cinereus (Goldfuss), Lone Pine Sanctuary, Brisbane, 26.ix.1955, F. A. Perkins coll. .
Female—Dorsum with single, small anterior (postcapitular) shield, which is rather longer than wide, and with a distinct row of heavy punctae on either side. Four setae, of which the external pair is longer, flank this shield. Remainder of dorsum covered with closely annulated cuticle, the contours being as shown; without any medial pattern as in A. enoplus. Dorsal setae as follows: two small setae mid- dorsally, a transverse row of four similar setae further back, and five pairs of longer marginal setae, the anterior pair of which is set above the two pairs of setae. in front of coxae III. Length of body 425-4444. Venter: Capitulum with usual pair of setae in posterolateral corners. Inner surface of coxae I and II hollowed and striate; with single pair of setae between coxae I and If. With two pairs of longer setae above coxae III. Apodemes of coxae IV stronger than those of III, and both pairs separated by a short median longitudinal sclerotization. Four setae in a line between coxae III, and four in a square between coxae IV. Anus longitudinal and subterminal, with one shorter anterior and one longer posterior pair of adanal setae. . Vertral cuticle similar to dorsal, with two pairs of setae posteriorly. Legs: Tarsi I and If with caruncles and usual recurved seta dorsally. Apart from the tarsi, the only movable segments of legs III and IV with setae are the basal and penultimate segments of lez Ill. Tarsi III and IV with setal pattern similar to other species of genus.
A SUMMARY OF THE ATOPOMELINAE,
Male.—Dersum and anterior half of venter as in female. Length of body 438—467u. Apodemes of legs III and IV T-shaped, those of IV being much the stronger. Genitalia behind coxae IV, set in sclerotized ring with two lateral setae. Intromittent organ well sclerotized, quite short and projecting backwardly. Anus flanked by two sclerotized areas, each with a short seta anteriorly and minute sucker posteriorly. Apex of abdomen slightly indented and flanked by five pairs of setae, the central pair being
very short. Legs III as in female. Leg IV swollen, with setae on tarsus as shown. Caruncle IV much smaller than III.
Text-fig. 1.—Austrochirus perkinsi, 0. sp. Left, venter of female. Right, dorsum of female. Inset above, dorsal shield of A. queenslandicus Womersley. Inset below, anus of female A. enoplus Domrow in lateral view.
Text-fig. 2.—Austrochirus perkinsi, n. sp. Venter of male.
Remarks—Mr. P. J. O’Sullivan recorded a severe outbreak of mange due to Notoedres cati (Hering) in the same sanctuary (Minutes of the Hntomological Society of Queensland for December, 1949), but A. perkinsi is the first native mite to be recorded from the koala. The new species is closely related to A. queenslandicus Womersley,. both possessing a simple dorsal shield and annulated cuticle. They may be separated on the shape and pattern of punctae on the dorsal shield, the sclerotization of coxae III and IV, and the genitalia and posterior legs of the male. The other two
BY ROBERT DOMROW. 43
species of the genus, A. sminthopsis Womersley and A. enoplus Domrow, have lateral accessory lobes to the dorsal shield and modified cuticular patterns, especially in the former.
CAMPYLOCHIRUS Trouessart. CAMPYLOCHIRUS CHELOPUS Trouessart, 1893 (genotype).
I have already (1956) redescribed this species, but Dr. R. F. Lawrence, who is at present engaged on groups other than the Listrophoridae, has asked me to clarify the position regarding one of his species. Ameng some listrophorid material sent to him from the Trouessart collection in the Muséum National d’Histoire Naturelle in Paris were specimens labelled as from an African rodent, Cricetomys gambianus (Waterhouse), which he deseribed (Lawrence, 1956) as a new monotypic genus and species, Cricetomysia andréi.
After this paper was published, he received a separate of my redescription (1956) of the genotype of Campylochirus from the Tasmanian phalangerid, Psewdo- cheirus convolutor (Oken), and began to suspect that the two species were at least congeneric. Since then we have exchanged specimens, and these have proved to be conspecific. There is no doubt that the syntypes of Cricetomysia andréi are also the syntypes from which Trouessart made his original description of Campylochirus chelopus in 1893, but how the labels became mixed is conjectural. Cricetomysia andréi Lawr. is thus an objective synonym of Cumpylochirus chelopus Trt.
Three other specific names have been traditionally associated with this genus (Radford, 1950), and may be conveniently considered here. Through the courtesy of Dr. Mare André, I have been able to examine the syntypes of Campylochirus adherens Trouessart, and these have proved to belong to the African genus Listrophoroides Hirst. As the species is unrecognizable from the published data, it is redescribed below.
Ewing (1929) synonymized Chirodiscoides Hirst (monotypic for C. caviae Hirst) with Campylochirus without stating any reasons. It is now clear that his assumptions were wrong, and that he had not seen authentic material of the genotype of Campylochirus. The two species here included in Chirodiscoides are distinct, and possibly closer to Listrophoroides than Campylochirus.
The third name to be considered is Campylochirus latus, ascribed to Trouessart (without date) by Radford. As a result of correspondence with Dr. Radford and a search through the literature, this name may now be placed as a nomen nudum. Campylochirus thus contains only the genotype, C. chelopus Trt.
ATELLANA, Nl. g..
Diagnosis —Atopomelinae with three dorsal shields (somewhat reduced in female) ; posteapitular shield anteriorly with narrow, transverse frontal lobe. Coxae II and Ili closely approximated, with numerous heavy retrorse spines at posterior margin of clasping apparatus. Leg IV of male enlarged, with modified caruncle. Anal suckers present in male. Nymph with postcapitular shield only; otherwise similar to female. With two attenuate tracheal tubes in all stages. Genotype: A. papilio, n. sp.
The new. genus may readily be separated from all known atopomeline genera by its characteristic dorsal shields (particularly the frontal lobe) and the spines behind the clasping apparatus.
ATELLANA PAPILIO, N. Sp.
Types: Holotype male, allotype female and morphotype nymph in Queensland Museum, Brisbane; paratype male in B.M. (N.H.). All specimens from fur on the thighs and rump of the phalangerid Trichosurus vulpecula (Kerr), D’Aguilar Range, S.E. Queensland, 1.iv.1957.
Maile—Dorsum: A frontal lobe, which appears narrow in dorsal view but more extensive laterally, precedes the anterodorsal (postcapitular) shield, and masks the capitulum, producing a characteristic hunched facies. Anterodorsal shield surrounded by four setae, one pair of which is in the longitudinally striated marginal cuticle, and the other in the posterolateral corners of the shield. Middorsal shield broad and
44 A SUMMARY OF THE ATOPOMELINAE,
with two pairs of posterolateral setae. Postdorsal shield almost entireiy divided medially by band of transverse striations; with eight setae arranged 2.4.2. Length of body 378-3884. Venter: Capitulum almost covered by frontal lobe of anterodorsal shield, but of similar structure to A. perkinst above, as are the structure of legs I and II and the clasping apparatus. Immediately behind coxae II a transverse row of several strong retrorse spines. Two setae above coxae III and a further seta above these. Internal apodemes of coxae III and IV very strongly sclerotized, in form of a butterfly. With four setae in arc between coxae III and two on the triangular lobes between coxae IV and genitalia, which have two minute setae posteriorly. Four setae between genitalia and anus, which is flanked by two small suckers. Apex of abdomen irregularly sclerotized, with four pairs of setae, of which one is very much stronger than the other three. Leg III as in female, with short seta on penultimate segment. Leg IV swollen, with caruncle weak and slender compared with that of tarsus III.
Text-fig. 3.—Atellana papilio, n. g., n. sp. Left, dorsum of male. Right, venter of male.
Female.—Frontal lobe and antercdorsal shield as in male. Length of body 448uy. Mid- and postdorsal shields reduced, and without setation. Laterally with longitudinal, and postdorsally with transverse annulations; setation as shown. Anus terminal, with two internal sclerotizations and two pairs of adanal setae. Capitulum and legs I and II as in male. Legs III and IV similar in size. Ventral surface not clearly visible, but probably with four setae between coxae III and two between coxae IV.
Nynvph.—bDorsally only with frontal lobe and anterodorsal shield flanked by four setae. Otherwise generally as in female adult. Body length 420u. The nymph illustrated is somewhat distended, being ready to moult, and containing a full-grown but weakly sclerotized male.
CytTostErHtm Domrow. The holotypes of the five species of this genus which I described in these PROCEEDINGS in 1956 have been transferred from this Institute to the collection of the Queensland Museum, Brisbane.
NEOLABIDOCARPUS Gunther. NEOLABIDOCARPUS BULOLOENSIS (Gunther, 1940).
Gunther recorded placing the “type specimen” of Labidocarpus buloloensis in the School of Public Health and Tropical Medicine, Sydney, and later erected a new monotypic genus (Neolabidocarpus) for this species, at the same time dividing the Listrophoridae into four subfamilies, Neolabidocarpus being placed in the Labidocarpinae.
BY ROBERT DOMROW. 45
Through the courtesy of Mr. D. J. Lee, I have been able to examine the sole specimen of this species (from Thylogale coxenii Gray, Gunther det.) in the §.P.H.T.M. It is not labelled as type, but certainly belongs to Gunther’s species. This specimen is a late nymph and is figured and described below. It is a typical member not of of the Labidocarpinae, but of the Atopomelinae, legs I and If not being greatly
Text-fig. 4.—Atellana papilio, n. g., n. sp. Lateral view of female.
Text-fig. 5.—Atellana papilio, n. g., n. sp. lateral view of preadult nymph, slightly distended, enclosing an adult male.
Text-fig. 6.—wNeolabidocarpus buloloensis (Gunther). Lateral view of holotype nymph.
flattened, and possessing definite caruncles. The coxal apparatus, as shown in Gunther’s figures, is also typical of the Atopomelinae. Since the holotype is a nymph, and the remainder of the material was destroyed during the war (Gunther, in litt.), it appears best to keep this genus and species apart until fresh adult material proves them valid or otherwise.
46 A SUMMARY OF THE ATOPOMELINAE,
Redescription of holotype nymph.—With single anterodorsal shield flanked by two pairs of setae. Remainder of dorsum covered by striations with contours and setation as shown. Anus terminal, with two internal sclerotized bars and two pairs of adanal setae (this type of anus is also present in the female of Awustrochirus enoplus, see inset). Capitulum and legs I and II typical, with recurved seta dorsally on tarsi I and II. Clasping organ not clear in detail, but typical of Atopomelinae; probably with pair of setae between coxae I and II. With pair of setae above coxae III and a further seta above these. Coxae III and IV also not clear, but of general atopomeline facies. Legs III and IV with usual four movable segments, the setal pattern of the (foreshortened) tarsi being typical of cther atopomeline genera. Body length 370u.
LISTROPHOROIDES Hirst.
Diagnosis.—Atopomelinae with three dorsal shields which cover entire dorsum, apart from apex of hysterosoma. Anterior dorsal (postcapitular) shield longer than broad, flanked by two small setae and lateral sclerotized zones which serve for the attachment of legs i and II. Middorsal shield subquadrate, with four setae along anterior margin. ostdorsal shield longer than broad, always with seta in each anterior corner and es pairs of setae on dise of shield, though additional setae may sometimes be present marginally. Capitulum with two basoventral setae. Legs I and II incrassate, with one strong seta dorsally on fused apical segments, and provided with caruncles. Clasping organ between coxae I and II always with two transversely striate areas, between which are a pair of setae. Two attenuate tracheal tubes present. Genitalia of female between coxae III and preceded by a sclerotized arc; with two pairs of anterior setae, two pairs of suckers and one pair of posterior setae. Coxae III with three setae. Legs III and IV not enlarged; with four movable segments. Penultimate segment of leg III with small dorsal seta. Dorsobasal seta on tarsus IV weak. Male genitalia between coxae III and IV; with one pair of anterior setae, two pairs of suckers and two pairs of posterior setae. Penis usually short, but exceedingly long in L. mastomys. Coxae III with three setae. Anus without suckers, but flanked by two setae. Posterior body lobe variable, but typically with three pairs of stalked setae, of which the median pair is the strongest. Leg IV somewhat enlarged, with dorsobasal seta of tarsus very strong and elongate. Tarsi IV also with two inner apical sclerotized points and termina! caruncle. Genotype: L. aethiopicus Hirst by monotypy.
The genotype has recently been redescribed and refigured (Lawrence, 1956), thus putting this genus on a firm basis. A second species, Ll. expansus, was described by Ferris (1932), who stressed the form of the anterior legs and the lack of spurs on coxae III. However, the former character is only of specific value, and the spurs described by Hirst for the genotype are artefacts (Lawrence, loc. cit.). Thus Marquesania Womersley, 1943, monotypic for Ferris’s species, becomes a synonym of Listrophoroides. :
Apart from LL. oryzomys, an American species which has been transferred to Chirodiscoides below, there are now fifteen names referable to this genus. A close study of these species has revealed a rather tangled situation, hence the full diagnosis above. BHleven species (nine African, one Ceylonese and one semi-cosmopolitan) are here recognized as valid.
Key to species of Listrophoroides, 1. Body very broad, terminating in two or four exceedingly long setae; postdorsal shield
reduced ini females On ws 2 thy Sr SClae rere cteteelateiencneteicenenc ir) ened iiellelcieiokceaiei onaitel ieee naan 2. Body quite slender, never terminating in long flagellate setae; postdorsal shield not reduced oa FESOTENIE, (Orn, IMENTAL) (EOE Thy CONGO) 5 ocanccocobacconongobonbounUnoo DO OON 3
bo
Female with apex of hysteroscma lacking pronounced conical process; postdorsal shield - evenly sclerotized. Posterior body lobe of male with three pairs of stalked setae, the MIECCIAN MD AnD CLUS sev CTVAES UL Ol) Same leicusns il MencneiennAaielsien Meek enenetenien ai eckeitaiiisiele nes .. bathyergians.
Female with apex of hysterosoma with large conical process; postdorsal shield wiih two heavily sclerotized areas laterally. Apex of abdomen of male with subquadrate shield bearine- ar flacellatessetan in) ealchy postemorNconner =). eee leineiene eerie eumpti.
BY ROBERT DOMROW. 47
3. Dorsl shields with very regular pattern of scales like those of fish or snakes; penis very NO See rarnet trae tee) Sate yet cae cleanness odie foley cated SANDS anadodts. a uMuayfetlted ye oop Stroy yultetint aqcemalkaye) fete) las mastomys. Dorsal Saige yr Bimo@WMEeIp WEAN S TOSS! Were SOOKE scococccsccnuvcosunccucuuaudad 4.
4. Dorsal shields heavily sclerotized and roughly pitted to produce a sponge-like effect; venter of hysterosoma of female entirely covered by coarse, pointed papillae .. africanus. Cuticle of dorsal shields otherwise; venter of hysterosoma normally striate and typically WHTAOIE TORN ONNEK SS TG cose Gime oln G.rora 6 Oro OR oie ice GIceee SRS icin Pact hOncE Cha icity Decne Cec ecu eee oa SP De IDersal siglals wiliin chisbaer Iliteene SibeenelOMs Gocoscoodsooe0cccuducocccauuunguGonuad 6. IDOREA Saiglels ay MnO. ine ATe GUSIENHIOINS:. Gaoogoeo soup oo pldod bcoo no Uden oO eclol Old. o Dore 9. 6. Striations of dorsal shields irregular, and not evenly spaced and transverse; middorsal
oO
Sinielél jowoackee joOsteiclomhy Waren enmesrelorbhy SoscoscagcobobuvavocduonoungpdoonDOUDE Ts Striations of dorsal shields evenly spaced and transverse; middorsal shield narrower WOSKCIIORI NBM Mee ANCE IOM iy Weewey stare cens: seers skeen sate. cys cat les tobi oriay oleh ewe al ichcivel evista sce Je coy et etlavievie) site ceevauate) 8
7. Postcapitular shield flanked by two pairs of strong setae; body setae strong; venter of hysterosoma of female without tubercles; coxae III of male simple; posterior body lobe WERIRIK? COIR CIO” » Bee a isn rorercrcle a. oeo cCRC CHE Rey Re Een ete econ “aren Nica: CRC ten Farce oS Seo mee adherens.
Posteapitular shiela flanked by two pairs of very weak setae; body setae weak; venter or hysterosoma of female with several drop-shaped tubercles posteromedially; coxae IIl of male produced inwardly to form two sclerotized processes; posterior body lobe StrOMahy Seleroiniwecl eimGl welll clemineg! ssoococasaoococtcoudnodnaouroeeoded lemniscomys.
8. Striae on dorsal shields very distinct; discrete and crescentie anteriorly and laterally, but transverse medially and posteriorly; striations of clasping organ not reaching Ievitereail GCkSSs Cie COpeyey IL elvaVOl TOL 5 Beach oicenl den jelolo Srtea, Ome loiclO oCrOrcucricaa Ohare Saaioio te Ginn leggadilla.
Striae on dorsal shields weaker (sometimes lacking on middorsal shield), and evenly transverse; striations of clasping organ reaching extreme lateral margins of coxae Flite ARO CHES rare ert acdyr sh sBenspstarichtrcptcyatiem eto isaieuicuie) skein selenite shee feet oo aus euslarious) sPeledsue el ebeake) Schesicansystecats expansus.
9. Lateral margins of hysterosoma serrate; female with posterior margin of middorsal shield even, and venter and dorsal apex of hysterosoma non-striate; male with expanded posterior body lobe with four short and two long stalked setae ........... aethiopicus.
Lateral margins of hysterosoma smooth; female with posterior margin of middorsal shield armed with stout median spine; venter of hysterosoma with longitudinal striae, and apex dorsally with transverse striae; male with posterior body lobe not expanded and vglulameet 0 Ollcgek OUI el OMG) WSCLA CE aie intua cies nucde ave cate mc mete ieee yr er saan esos Ge a womersleyi.
LISTROPHOROIDES ADHERENS (Trouessart, 1893), n. comb.
Description of female—A slender, well-sclerotized species; body length 378—-3892u. Anterodorsal (postcapitular) shield slightly longer than broad, flanked laterally by two pairs of setae above insertions of legs I. Middorsal shield subquadrate, with irregular scale-like markings and without setae. Postdorsal shield longer than wide, with rather more distinct scale-like markings, and an anterior and posterior transverse row of four slender setae. Apex of hysterosoma triangular, with minute apical point; not covered by postdorsal shield, but with two slender setae. Venter: Capitulum with two basal setae. Genitalia placed between coxae III, with usual three pairs of small setae and two pairs of minute suckers. Posteroventral margins of hysterosoma covered by lateral lobes of postdorsal shield. Medially with fine longitudinal striae, but without tubercles; with two seta posteriorly. Anus longitudinal and subterminal, flanked by three pairs of slender setae, the posterior pair being much the shortest. A tracheal system similar to that of L. expansus figured below is present. Legs: Legs I and II typical of subfamily. Inner surfaces of coxae I and II hollowed and striate, with a pair of small setae between the two striate zones. Coxae I] with stronger seta on posteroventral margin (this seta probably represents the outer pair of the six seta normally present flanking the postcapitular shield and along the anterior margin of the middorsal shield). Coxae III with single anterior seta and flanked by a larger and a smaller seta. Coxae IV without setae. Legs III and IV with usual four movable segments; penultimate segment of leg III apparently without dorsal seta.
Description of male—As in female dorsally and anteriorly, but somewhat smaller; length of body 350-360u. Genitalia set between coxae IV, with usual three pairs of small setae and two pairs of minute suckers. Anus longitudinal and subterminal, with pair of small adanal setae anteriorly. Posterior body lobe simple, with extremely shallow posteromedian lobe; with two pairs of long slender ventrolateral setae and one pair of small terminal setae; also with two setae arising dorsally, being the outer pair of the posterior row of four setae on postdorsal shield. Legs III (including coxae)
48 A SUMMARY OF THE ATOPOMELINAE,
as in female. Legs IV somewhat enlarged, with dorsobasal seta of tarsus very strong and much elongated. Tarsus IV with two minute ventroapical spurs. Caruncle terminal.
Remarks.—Trouessart (1893) placed this African species in the genus Campy- lochirus, but it is unrecognizable from the available descriptions. (The specific name was spelt adhaerens by Trouessart in 1917, but this is regarded as an erroneous
B
Text-fig. 7.—Listrophoroides adherens (Trouessart). Left, venter of female. Right, dorsum of female.
Text-fig. 8.—Listrophoroides adherens (Trouessart). Venter of male. Inset at right,
middorsal shield of Listrophoroides ajricanus Radford; below, outline of posterior margin of mid@orsal shield of female of Listrophoroides womersleyi (lawrence).
subsequent spelling.) Through the courtesy of Dr. Marc André I have been able to reexamine Trouessart’s ten syntypes from Anomdalurus fraseri erythronotus Milne Edwards from the Congo, Dybowsky coll. The specimens have been remounted successfully on two slides which have been returned to the Muséum National d’Histoire Naturelle in Paris. One slide (with the original labels) contains the lectoholotype
BY ROBERT DOMROW. 49
female and the lectoallotype male, and the other six paratype females and two paratype males. The species is a typical member of the genus Listrophoroides, and may be separated from the other species of the genus by the above key. Lawrence (1956) did not include it in his revision of Listrophoroides, although he had examined the material.
LISTROPHOROIDES AETHIOPICUS Hirst, 1923.
This species has been discussed above, but it should be noted that in Hirst’s figure the third (posterior) pair of genital suckers are artefacts, and that the second pair of postgenital setae are not depicted. In Lawrence’s figure (1956) the adanal setae are lacking. I attach no significance to the minor variation in the posterior body lobe and dorsobasal seta of tarsus IV in the male.
LISTROPHOROIDES AFRICANUS Radford, 1944 (emend.).
This species was described from the same host and locality as L. mastomys Radford. The slide I have examined is labelied as containing three female L. mastomys, but really contains one female L. mastomys and a pair of L. africanus. Vertrally the male may be recognized by the strongly sclerotized, fused coxal plates of legs III and IV, which are extended inwardly, though not meeting medially, behind coxae IV to flank the genitalia posteriorly. The clasping apparatus is striate. The most striking character of this species is, however, the texture of the dorsal shields. These are heavily sclerotized, and with typical fine punctae. However, this punctation is overlaid by very numerous, much larger and deeper pits of variable size and shape, which are evenly spread over the entire surface, producing a rough, areolate and almost sponge- like appearance. The female is in lateral view and freshly moulted, but has similar dorsal shields to the male. The venter of the hysterosoma is entirely covered with strong, outstanding tuberculate processes. Lawrence (1956) in his key says that in L. mastomys the female has the “ventral surface roughened with large sharp granules”, and probably examined this same slide. However, he has associated the sexes wrongly, since in the female in question the dorsal shields have the same characteristic texture as the male of L. africanus. As the name of the genus is of masculine gender, the termination of the specific name has been amended.
LISTROPHOROIDES BATHYERGIANS Radford, 1939.
This characteristic species and L. zumpti form a distinct group found only on bathyergid rodents, the other species being typically from Muridae. These two species may be recognized by their broad bodies and the possession of long terminal flagellate setae. Lawrence (1956) says that both lack striae on the clasping apparatus between coxae I and II, but this is incorrect. Under oil immersion, typical striae are present both in Radford’s types and in specimens of L. zumpti with collection data as in the type series. This character appears to be constant throughout the subfamily, but should be checked in Centetesia Lawrence.
LISTROPHOROIDES DASYMys Radford, 1942.
This species, which certainly belongs to Listrophoroides, is known only from a single male. As the description contains no detail of value in determining its specific status, and the figure is semidiagrammatic and inaccurate, I have left this form as a species inquirenda. It will undoubtedly prove to have striae between coxae I and II, two pairs of small genital suckers, and 4-segmented legs III and IV. The description calls for a long seta on leg II, but in the figure it is leg I that has a long seta. The dorsal surface is not described.
LISTROPHOROIDES EXPANSUS Ferris, 1932.
Synonymy.—Womersley (1943) described and figured Marquesania expansa form queenslandica from rats from S.H. Queensland on the basis of the lack of striations on coxae I and II, and the absence of a “tooth” on leg I. However, he was mistaken on both points, and the form is here regarded as a synonym of Ferris’s species. Coxae I and II in all stages are obviously striate as illustrated. An oval, punctate sternal area is always present between the striations of coxae II. The “tooth” on
50 A SUMMARY OF THE ATOPOMELINAF,
leg I requires further explanation. In dorsal and particularly in ventral view, leg I appears to have a sclerotized process, but this is due to observing a narrow hyaline lobe from end to end. In dorsolateral view the hollowed inner surface of this lobe may be seen to clasp the shaft of the hair of the host, the free segments of legs I and II passing right around the hair. The mode of attachment is similar to that figured by Lawrence (1954) for Tenrecobia pauliani (the original spelling “pauliana”’ is in contravention of Article 14, and thus subject to automatic correction) from Madagasear. Some other details of Womersley’s description also need correction. The anterior dorsal (posteapitular) shield is not hroadly transverse, but decidedly longi-
150»
Text-fig. 9.—Listrophoroides expansus Ferris. weft, dorsum of male preadult nymph. Centre, dorsum of female preadult nymph. Right. venter of female preadult nymph. Below, dorsum of penultimate nymphal stage showing suture line.
tudinal, with distinct lateral margins and setae arranged as figured for the nymph. The areas to the side of this shield serve for the attachment of legs I and II. The inverted Y containing the genitalia of the adult male is heavily sclerotized cuticle rather than a definite structure.
A second synonym of this species is Listrophoroides trdgdrdhi Radford, 1940, the striking similarity between the published descriptions being confirmed by the study of specimens kindly lent to me by Dr. Radford. Of the available figures, those of Ferris are the best.
Distribution.—This species is apparently almost cosmopolitan on Rattus rattus (Linné) and R. norvegicus (Berkenhout), and has probably spread onto native rodents from these two species. It has been recorded from Sierra Leone, Uganda, Ceylon
-
BY ROBERT DOMROW. 51
and the Maldive and Marquesas Is. It is also common on R. assimilis (Gould) in S.H. Queensland, and may now be recorded from North Queensland as follows: R. rattus, Sundown, 23.viii.1956, and Innisfail, 9.x.1956, and &. assimilis, Bartle Frere, 13.11.1957. Recent material from R. gestroi gestroi (Thomas), Porebada Village, Port Moresby, Papua, 19.xi.1956, comprises preadult nymphs of both sexes. Hach nymph is still enclosed in the skin of the penultimate nymphal stage, which shows a distinct central longitudinal suture from the anterior edge of the middorsal shield to the apex of the hysterosoma, which may be still intact or gaping widely. In one specimen the final nymph came out of its old skin during mounting procedure. Womersley only described the adults, and although the present nymphs are quite pale, they are adequate for illustration and are described below.
Description of preadult male nymph.—Length 350-362y. Anterodorsal (post- capitular) shield longitudinal, slightly wider posteriorly, and flanked by two small setae. Suture between postcapitular and middorsal shield well marked, with four setae arranged along it. Middorsal shield subquadrate, with few scale-like markings. Third (postdorsal) shield covering remainder of dorsum, with about eight setae as figured. Apex of hysterosoma without well-developed accessory lobe of adult, but with six fairly strong setae. Venter: Genitalia small and poorly developed, situated between coxae III and IV, and without any inverted Y sclerotization. Legs as in preadult female nymph, but leg IV slightiy thicker.
Description of preadult female nymph—Length 374-3854. The structure of the anterior two pairs of legs is described above. Anterior half of body as in preadult male nymph. Postdorsal shield constricted medially, with transverse markings, and flanked by lateral cuticular areas with longitudinal striations; with six setae. Venter: Two zones of striae between coxae I and II, the former with small seta near inner posterior margin, and latter extending to extreme lateral margins of body. Radford’s interpretation of these normal striae as a “toothed semicircular process” is incorrect. Oval, punctate sternal area between coxae II. Genitalia between coxae III, with setae and minute suckers arranged about an inverted Y. Anus subterminal, flanked by about six small setae. Legs III and IV not greatly enlarged. With distinct tracheal system on either side, consisting of a spherical atrium between coxae I and II opening into a single trachea, which becomes thicker along its course, and thins again posteriorly. A similar tracheal system was illustrated by Hirst (1921) for Listrophoroides aethiopicus.
Description of penultimate nymphal stage—Length in distended condition 409—432u. Similar to preadult female nymph anteriorly and ventrally. Dorsum with postcapitular shield and weakly defined middorsal shield. Remainder of body covered with striations which are longitudinal midlaterally and transverse posteriorly. With central suture- line along dorsum, through: which the preadult nymph emerges. Legs III and IV slightly thinner than figured for preadult nymphs. The earlier, rather similar nymphal stage with six legs described by Ferris has also been seen. ;
LISTROPHOROIDES LEGGADILLA Radford, 1947.
This form was originally described as a full species from Ceylon, but may prove to be a variant of the cosmopolitan L. expansus. Both forms are of identical facies and setation, particularly as regards the shape of the dorsal shields and their texture, and the posterior body lobe and the form and setation of the legs in the male. The postdorsal shield is narrower than shown by Radford, and the ventrolateral hystero- somal shields, if present, very weakly defined and with margins indiscernible. The transverse markings on the dorsal shields are much more distinct than in L. expansus, but are not crescentic as depicted by Radford, except laterally and anteriorly. The discal markings, especially posteriorly, are transverse and evenly spaced as in L. expansus. The Y-shaped sclerotization around the male genitalia is not well defined, and the striae on the clasping apparatus do not reach the extreme lateral margin of the coxae as in L. expansus, but finish evenly, well in from the edge of the coxae, along a longitudinal line as figured by Radford.
52 A SUMMARY OF THE ATOPOMELINAE,
LISTROPHOROIDES LEMNISCOMYS Radford, 1940.
Both this species and Marquesania imbricata Lawrence, 1954, were described from Lemniscomys in Uganda and Zululand respectively. Comparison of both sexes of Lawrence’s species from the type series and of Radford’s from the type host has revealed complete identity in cuticular pattern and fine detail, including the two - characteristic crescentic marks at the anterior edge of the middorsal shield, the large bases to the gnathosomal setae, the posteromedian ventral tubercles of the female and the posterior body lobe of the male. WM. imbricata is therefore considered a synonym of L. lemniscomys.
LISTROPHOROIDES MASTOMYS Radford, 1940.
This species may be readily recognized by its evenly scaled cuticle, which is a reminiscent of snake or fish skin. Some rather strong longitudinal lines are present laterally on the middorsal shield. Specimens of both sexes from the type series of this species agree in cuticular pattern and in all fine detail with the full description of Marquesania elongata Lawrence, 1951, and possess in the male both the characteristic posterior body lobe and the ventrolateral, inwardly directed points behind coxae IV. Lawrence (1951, 1956) is in error in saying coxal striae are absent. The enormously long penis is characteristic of the species, but apparently could not be seen by Lawrence, whose only specimen was obscured by a hair. The two species are here considered identical. The females referred to this species in Lawrence’s key (1956) are really L. africanus (q@.v.), which was originally collected from the same host and locality.
LISTROPHOROIDES WOMERSLEYI (Lawrence, 1951).
This species may be immediately recognized by the characteristic pattern of cuticular striae at the apex of the hysterosoma of the female, and (at least in the female) by a distinct pointed median process (not shown in Lawrence’s figure) on the posterior margin of the middorsal shield. Two nymphs examined show a longitudinal middorsal suture and dorsal shields similar to those figured above for L. expansus:
LISTROPHOROIDES ZUMPTI Lawrence, 1956. This species has been discussed under L. bathyergians.
CHIRODISCOIDES Hirst. This genus is monotypic for C. caviae Hirst, 1917, the widespread parasite of guinea-pigs, which originally came from South America. The species is well illustrated in Hirst (1922) and Lawrence (1956).
CHIRODISCOIDES ORYzZOMYS (Radford, 1954), n. comb.
This American species was originally described as a Listrophoroides, but has the following important generic characters in common with C. caviae: Males with four setae between coxae III and IV; genitalia flanked posteriorly by two setae and four minute suckers; anus surrounded by two setae and two large suckers; posterior body lobe well developed; leg III normal; leg IV enlarged; tarsus IV hooked distally, with two inner apical sclerotized points and subapical external caruncle. Both sexes with three dorsal shields, the middorsal being rather narrow. Females with postdorsal shield truncate, leaving posterior half of hysterosoma covered only by annulated cuticle. Radford’s species has therefore been reassigned as a second species of Chirodiscoides. Since his figure is incorrect in several details, the following supplementary data are given.
Male—Clasping apparatus striate between coxae II as well as coxae I. Dorsum with three shields as follows: Postcapitular shield deeply convex posteriorly, extending back to level of coxae II; flanked posteriorly by four setae. Middorsal shield very narrow medially, reaching back only to level of posterior edge of basal movable segment of leg II; straight posteriorly and concave anteriorly to accept postcapitular shield. Postdorsal shield covering remainder of hysterosoma and deeply cleft posteriorly. Penis slender and of moderate length, running forward and then turning abruptly backwards. Posterior body lobe with strong median cleft, the inner posterior
angles of the two lateral processes being turned inwardly; ventrally and four stalked setae laterally on each process.
BY ROBERT DOMROW.
53
With strong, rod-like,
transverse coxal apodemes between legs III and IV, that of IV being the thickest;
united medially by strong longitudinal strut similar pattern is illustrated for Austrochirus perkinsi above).
and enclosing four setae (a rather Legs III and IV with
Synopsis of the Subfamily Atopomelinae (Listrophoridae). (Genotypes listed first, followed by other species in alphabetical order.)
Genera and Species.
Host.
Locality.
ATELLANA, D.g. A. papilio, n.sp... at ATOPOMELUS Trouessart, 1917. A. locusta Trouessart, 1917 AUSTROCHIRUS Womersley, 1943.
A. queenslandicus Womersley, 1943 ..
A. enoplus Domrow, 1956
A. perkinsi. n.sp. Re oh
A. sminthopsis Womersley, 1954 CAMPYLOCHIRUS Trouessart, 1893.
C. chelopus Trouessart, 1893. ..
C. latus Be 55 CENTETESIA Lawrence, 1954.
C. tiptont Lawrence, 1954
C. tessellata Lawrence, 1954 CHIRODISCOIDES Hirst, 1917.
C. caviae Hirst, 1917
C. oryzomys (Radford, 1954) CRICETOMYSIA Lawrence, 1956.
C. andréi Lawrence, 1956
CYTOSTETHUM Domrow, 1956. C. promeces Domrow, 1956 C. charactum Domrow, 1956 C. nanophyes Domrow. 1956 .. C. pseudocharactum Domrow, 1956 C. trachypyx Domrow, 1956 LISTROPHOROIDES Hirst, 1923. . aethiopicus Hirst, 1923 . adherens (Trouessart, 1893) . africanus Radford, 1944 bathyergians Radford, 1939 dasymys Radford, 1942 . elongatus (Lawrence, 1951) expansus Ferris, 1932 imbricatus (Lawrence, 1954) . leggadilla Radford, 1947 lemniscomys Radford, 1940.. mastomys Radford, 1940
. trdgardhi Radford. 1940 . womersleyt (Lawrence, 1951) . zumpti Lawrence, 1956 MARQUESANIA Womersley, 1943. NEOLABIDOCARPUS Gunther, 1942. N. buloloensis (Gunther, 1940) TENRECOBIA Lawrence, 1954. T. pauliant Lawrence, 1954
SESESESESESESESESESE SSE iSns|
. queenslandicus (Womersley, 1943). .
Trichosurus. Neotetracus. Thylacis. Hydromys. Phascolarctos.
Sminthopsis.
Pseudocheirus.
Hemicentetes. Hemicentetes.
Cavia. Oryzomys.
Cricetomys (!).
Potorous. Potorous. Potorous. Potorous. Potorous.
Cricetomys. Anomalurus. Mastomys. Bathyergus. Dasymys. Aethomys. Muridae. Lemniscomys. Leggadilla. Lemniscomys. Mastomys. Rattus. Muridae. Otomys. Georychus.
Thylogale.
Ericulus.
Queensland.
China.
Queensland. Occasionally on Perameles. Queensland.
Queensland.
South Australia.
Tasmania. Nomen nudum.
Madagascar. Madagascar.
Widespread.
U.S.A. New combination.
Synonym of Campylochirus.
Africa (!). Synonym of Campylochirus chelopus.
Queensland. Queensland. Queensland. Also Tasmania. Queensland. Queensland.
Africa.
Congo. New combination.
Sierra Leone. emend. °
South Africa.
Uganda. Species inquirenda.
Natal. Synonym of LZ. mastomys. Widespread.
Zululand. Synonym of LZ. lemniscomys. Ceylon.
Uganda.
Sierra Leone.
Queensland. Synonym of L. expansus. Widespread. Synonym of L. expansus. South Africa.
South Africa.
Synonym of Listrophoroides.
New Guinea. Species inquirenda.
Madagascar. emend.
usual four movable segments (the long medial segment of leg IV in Radford’s figure
is weakly divided centrally).
Penultimate segment of leg III with small dorsal seta.
Tarsus IV hooked distally, with twe inner apical sclerotized points as in JListro- phoroides; caruncle set dorsally and subapically.
Female.—Anterior half of body as in male. to midway between level of coxae IV and apex of hysterosoma;
Postdorsal shield truncate, extending
quite concave
with two normal setae
54 A SUMMARY OF THE ATOPOMELINAE,
posteriorly. Apex of hysterosoma simple. Genitalia between coxae III. Legs III and IV of normal size; tarsus III with enlarged dorsobasal seta.
Acknowledgements. In addition to those mentioned in the text, I am grateful to Drs. I. M. Mackerras . and HE. H. Derrick for reading my manuscript, to Dr. K. H. L. Key for advice on some nomenclatural problems. and to Miss EH. Wood for her careful typing. .
References.
Domrow, R., 1956a.—Notes on Ausiralian fur-mites (Listrophoridae, Atopomelinae), with description of a new genus. Proc. LINN. Soc. N.S.W., 80: 191-200.
——§—, 1956).—The genera Campylochirus Trouessart and Austrochirus Womersley in Australia (Acarina, Listrophoridae). Proc. Linn. Soc. N.S.W., 80: 234-239.
Domrow, R., and SmitH, D. J. W., 1956.—Acarina from five hundred native mammals from Queensland. Proc. LINN. Soc. N.S.W., £0: 201-206.
EwiIne, H. W., 1929—A manual of external parasites. Bailliere, Tindal! & Cox, London. Page 44. i
HERRIS, G. F., 1932.—Hctoparasites of Marquesan rats. Bull. Bishop Mus., Honolulu, 98: 117-127.
GUNTHER, C. H. M., 1940.—A listrophorid parasite of the wallaby from New Guinea. Proc. Linn. Soc. N.S.W., 65: 3538-354.
, 1942.—Notes on the Listrophoridae (Acarina, Sarcoptoidea). Proc. Linn. Soc.
N.S.W., 67: 109-110.
Hirst, S., 1917.—On three new parasitic Acari. Ann. Mag. nat. Hist., (8) 20: 431-434. ————, 1921.—Notes on parasitic Acari. A. On the presence of a system of tracheal tubes in the families Sarcoptidae and Listrophoridae. J. Quweckett micr. Cl., 14: 229-232.
, 1922.—Mites injurious to domestic animals. Brit. Mus. (Nat. Hist.), Hconomic Series No. 13, 107 pp. , 1923.—On some new or little known species of Acari. Proc. zool. Soc. Lond., 971-1000. LAVOIPIERRE, M., 1946.—New records of Acari from Southern Africa and the Belgian Congo. J. ent. Soc. S. Afr., 9: 78-81. LAWRENCE, R. F., 1951.—New fur mites from South African mammals. Ann. Natal Mus., 12: 91-133. , 1964a.—Two new fur-mites from rodents. J. ent. Soc. S. Afr., 17: 38-46. —, 1954b.—Studies on the listrophorid mites (Sarcoptiformes) of Centetidae from Madagascar. Mém. Inst. Sci. Madagascar, 9A: 129-149. — , 1956.—Studies on South African fur-mitcs (Trombidiformes and Sarcoptiformes). Ann. Natal Mus., 13: 337-375. RADFORD, C. D., 1939.—Notes on some new species of parasitic mites. Parasitology, 31: 243-257. , 1940.—Notes on scme new species of parasitic mites. Parasitology, 32: 91-104. , 1942.—New parasitic mites (Acarina). Parasitology, 34: 295-307. 1944._New parasitic mites (Acarina) from rodents. Parasitology, 35: 161-166. , 1947.—Parasitic mites from snakes and rodents (Acarina Cheyletidae, Listro- phoridae and Laelaptidae). Proc. zool. Soc. London., 117: 228-240. , 1950.—The mites (Acarina) parasitic on mammals, birds and reptiles. Parasitology,
40: 366-394. , 1954.—Three new species of fur mites (Acarina: Listrophoridae). Riv. Parassit.,
15: 593-599. TROUESSART, HE. L., 1893.—Note sur les sarcoptides pilicoles (Listrophorinae). C. R. Soe.
Biol., Paris, (9) 5: 698-700. , 1917.—Troisi¢me note sur les sarcoptides pilicoles et description de genres nouveaux. Bull. Soc. zool. Fr., 42: 151-158. WOMERSLEY, H., 1943.—Australian species of Listrophoridae Canest. (Acarina) with notes on the new genera. Trans. roy. Soc. S. Aust., 67: 10-19. , 1954.--Two new species of ectoparasitic mites from pouched mice, Sminthopsis, from Australia. Rec. S. Aust. Mus., 11: 117-120.
5D
INHERITANCE OF OIL CHARACTERS IN EUCALYPTUS.
By L. D. Pryor, Parks and Gardens Section, Department of the Interior, Canberra, and L. H. Bryant, Division of Wood Technology, Forestry Commission of New South Wales.
(Five Text-figures.) [Read 30th April, 1958.]
Synopsis.
Examination of segregates from EH. cinerea x EH. Macarthuri and E. pauciflora x E. Robertsoni or E. dives, together with Fl hybrids between #. Maideni x EH. rubida, shows that recombination between oil yield and components on the one hand and morphological characters on the other occurs. Yield is sometimes determineaG in a far-reaching way in accordance with that of one parent. The variance of physical and chemical constants of oils derived from segregating hybrids is much greater than that of those for the parents. Oil constituents may be found in much greater quantity in some segregates than in either parent.
It has been evident that oil characters of Eucalypts, especially yield and the nature of their various constituents, are determined to a large extent by heredity. The review of the genus by Baker and Smith (1920) and their attempt to develop its taxonomy by the consideration of oil composition shows the high degree of oil specificity which species have sometimes been found to possess. On the other hand, something is also known about the variation within species largely as a result of the recognition of “physiological forms” by Penfold and Morrison (1927) in EH. dives. Such forms are more or less similar morphologically, differing mainly in the chemical nature of their oils. These have been found since also in many other species of Eucalypts as well as in other genera of the Myrtaceae.
A study by Willis (1951) of families planted in one locality, made up of several progenies from different oil varieties of H. dives from different localities, showed that within this species the characters of the parents were largely repeated in the progeny too. Bryant (1950) has summarized unpublished work carried out with Smith-White indicating that wide variations in oil yield occur within a number of commercially important species. Major constituents of the oils were also shown to vary within the species and also even within a single tree but there has been little study of the variation in minor components.
The biological significance of essential oils in plants has not yet been clearly established, although different theories have been advocated. Two main ideas may be mentioned. The first, held by James (1953) and others, suggests that in plants generally, constituents such as alkaloids or essential oils are produced as a by-product of metabolism and have no adaptive significance. The second, demonstrated in some plants by Dethier (1941) and held by Barber (1955) for Eucalypts (and oil or alkaloid bearing plants generally), is that the varying characters of the oils indicate part of a system which is of distinct adaptive value by determining the palatability or resistance to insect pests. It has not yet been established for Eucalyptus that palatability to insects is influenced by the chemical nature of the essential oil, but if this is so one could imagine through time a sequence of changes both in oil composition and insect variation, leading to a series of alternating changes in closely adaptive responses in both plant and insect. Dethier (1941), using pure compounds found in the oils of some species of the Rutaceae and Umbelliferae, was able to induce Papilio larvae to eat filter paper treated with them and so indicate positive attraction by them for these insects. In Hucalyptus strong preferences by leaf-eating insects are
PROCEEDINGS OF THE LINNEAN Society OF NEw SoutH WALES, 1958, Vol. lxxxiii, Part 1.
56 INHERITANCE OF OIL CHARACTERS IN EUCALYPTUS,
already known, and in one or two combinations there is evidence that this is an inherited character (Pryor, 1953). It is possible that the major oil constituents in Eucalyptus, while of great consequence in a similar system in some earlier evolutionary period, may now be of little importance, and the real significance as far as insect attack is concerned may rest with quantitatively minor constituents.
There is considerable interest, therefore, both from the point of view of evolutionary genetics and in understanding physiological forms, in gaining knowledge of the mode of inheritance of oils in Hucalyptus. The study might also provide basic information which could lead to very important results in applied work, such as in the control of insects feeding on Hucalyptus on the one hand and in the Hucalyptus oil industry on the other. Investigation can proceed some distance by raising progeny from open pollinated natural hybrids which give access to segregating groups of individuals containing recombinants derived from pairs of parent species. This will permit some deductions concerning the inheritance of oil characters.
Method.
Combinations of parent species were selected which showed some strongly contrasting characters both in oils and morphology. Open pollinated progeny raised from naturally occurring hybrids have been examined at about the age of six years. Progeny of the parents of the same age, raised at the same time, have been compared. The offspring of parents (supposedly the “pure” species) are not necessarily of precisely the same stock which led to the production of the hybrids, and there is a potential source of error here which imposes some limitations on the interpretation of the data, and may account for some minor anomalies which have been found.
The crude oil samples were obtained by steam distilling 10 lb. of green leaves and small twigs collected in the same way and in the same position from each of the trees. Approximate weighing to a little more than 10 lb. with a spring balance was earried out in the field, and a more precise weighing to reduce the sample to 10 lb. + 3 02z., was made in the laboratory. The leaves were steam distilled to obtain the first oil sample. The physical and chemical analyses were carried out by one of us (Bryant). Two sets of data were compiled. Firstly, the constants usually calculated for essential oils were established, particularly specific gravity, refractive index, optical rotation and saponification number. Secondly, by a method of circular chromatography (Bryant, 1955) using glass coated with inagnesol, an assessment of most of the oil components was made. The oils were developed with n.hexane containing 15 parts by volume of ethyl acetate and then sprayed with concentrated H.SO, or examined under ultra-violet light. Most of the oil constituents reacted with the H.SO, to give characteristic colours. Cymene and the pinenes did not react satisfactorily and, although they are known to occur to some extent in these oils, their proportion was not assessed. To assess recombination between oil features and other characters, measurements of selected leaf features were made as well. In some, the leaf shape as indicated by the length-breadth measurement was used, and in others the angle which the primary veins made with the midrib. Transformation of the length-breadth figures to a logarithmic scale results in reducing the variance of the data for the parents in each case to more nearly the same level, and makes the relationship clearer between the various groups and intermediates.
A small amount of material was also available from Fil hybrids produced by manipulation, and this, though limited in extent, gives some additional indications of the inheritance pattern.
E. cinerea x H. Macarthuri.
The hybrid H. cinerea x H. Macarthuri is found naturally from time to time where these two species meet in the field. Two segregating progenies were raised from two separate hybrid trees of this combination found at Paddy’s River on the Hume Highway near Marulan, N.S.W., from which open pollinated seed was collected. The parent trees differ widely in morphological and oil characters. Table 1 shows the principal physical differences between the two species. Table 2 and Figures la and 1b show the range of variation of oil and morphological characters within the
BY L. D. PRYOR AND L. H. BRYANT. ; 57
parent species and in the segregates. These latter show marked segregation and recombination of beth characters, and contain individuals which closely resemble either parent together with a series of intermediates between them.
~ TABLE 1. — E. cinerea. E. Macarthuri.
Juvenile leaves .. | Orbicular. Lanceolate.
Sessile. Sessile.
Glaucous. Green. Mature leaves .. | Sessile. Petiolate.
Opposite. Alternate.
Glaucous. - Green. Oil yield se .. | High (about 1:75% vol./wt.). Low (about 0:25%). Main constituents .. | High cineole (about 40%). Cineole nil.
Geranyl acetate (nil). Geranyl acetate (about 50%).
In the hybrid progeny 50/755a there are more segregates approaching FH. cinerea than #£. Macarthuri. In 50/755 they are approximately evenly distributed between the parental limits. It will be noticed that the quantity of oil produced in both hybrid progenies is within the range of the low-yielding parent (#H. Macarthuri), and there is not a single exception to this (Fig. la). This suggests, therefore, that
°. Sine nN ® @ e oF a ae e ; 2 aS x s S ; a x ad & fy come § * x ® = Q 2 ae AG) z 8 Ss x x s 8 5S 8 i : a = ae ; N x sep i fe > S x ® 0 x J se x 5 x ey 4 mx 4 a -2 = 7] 2 3 7 F o Leaf log “/a Lear Log. */a8 la &. cinerea - £ Macarthur 1h 4&ctherea - £. Macarthur s e s e
Fig. la.—Yield of oil in ml. per 10 Ib. of green leaf against juvenile leaf shape is shown. The “x’s” indicate hybrids. It will be seen that the leaf shape in the hybrid progeny ranges between either parent, but that the oil yield is entirely within the range of the H. Macarthuri parent.
Fig. 16.—Saponification number in relation to leaf shape shows in this particular progeny a tendency for the #. cinerea characteristic of low saponification number to persist in the hybrid progeny indicated by the ‘“x’s’, but there are some recombinants which have #H. cinerea leaf shape but saponification number equal to that of H. Macarthuri and one which is the reverse.
the factors determining quantity of yield in the H. Macarthuri parent are dominant in this combination, and they determine low yield. On the other hand, it will be seen that the amount of geranyl acetate in the oil assessed by saponification number, when compared in relation to the morphological character of leaf shape, shows distinct evidence of recombination. Hybrids 23 and 34, while having a leaf shape which
D
58 ‘ INHERITANCE OF OIL CHARACTERS IN EUCALYPTUS,
approaches that of HE. cinerea, have a saponification number which is closely comparable with that of H. Macarthuri, whereas, on the other hand, No. 16 has a leaf shape which is near the centre of the range of #H. Macarthuri, but has a much lower saponification number. In the data as a whole there is low correlation between leaf’ shape and saponification number, which suggests rather free recombination between these two characters (see Fig. 1b). Both hybrid progenies are somewhat limited, and a considerably larger population would be desirable to assess more accurately the pattern of recombination, and to determine whether there is any tendency for characters to recur in association in any degree, perhaps suggesting linkage.
In Table 2 the presence of the various constituents of the oils (excluding terpenes. such as the pinenes already mentioned which do not react readily with concentrated H.SO,) has been assessed by the chromatographic method mentioned above. It will be observed that cineole and geranyl acetate, which could not be detected in the parent #. Macarthuri and EH. cinerea oils respectively, are both present together in the oils of some of the hybrid individuals. In no case is there a hybrid oil where both these constituents are absent. Geraniol, present in small quantities in all
TABLE 2. Oil Constituents (Hacept Cymene and Pinenes) of cinerea, Macarthuri and Hybrids.
Fluo- Geranyl Hudes- Sesqui- rescent — No. Acetate. Geraniol. | Cineole. | Hudesmol. mene. terpene. Com- ponent.
| 5258 3
Mx x
x XX
E. Macarthuri. 64
XS 2S 08 OS os OK BK OX OS OK OS OK OS OK CK 2K OS
x x
oS ON OS 26 OS 3K OK OK OS OK OK OS OE OK RK OS OK OK OK OR x
for) or x OS OS BS BK RS OS OS MOK OS OK OK OX OS OK OK OK OK OOS KR KX KOK KKK OS OK OK OK OS Oh ES es 2S ES OS OS OST BS BS OS POON ES BS OS OM OM BS oS OS OS OS PS OS OS BS OS os O6 O46 OM BS 24 PS es OS OX | os Ps OS Oh OS PS OS ES OS OS BS ES PS OS eS OS OS OS OS eS “S 2S OS OS 8% OS OX OK OS EK OS OS OK OK OK OK SOS OS DK Oh 2G BS OS BK BS OS OS OM OS OS OS 2S OS OS OS OM OS OX PS Px 25 PS BS Om OS BX ES OK OC OS OS OK BS OS OS PS OS OS x x
x
nS pia |
| IxX|x x
ws o> oO || ! fl
nN co |
| Ix |
E. cinerea. 51 -
(o2) oi | |
par S 0 oOo @ lll |
|
| xxxxxxXxXxXxXxXXXXXXXXXX*X xxxxXxXxXxXxXxXXxXXXxXXXXXX*X De aE OX KEE XK KX XXX xxxXxxXxxXxXxXxXxXXXXXXXXXXX*X x Ibs allel lel bal bs 4] bal bal bal bal allt) bal -alle-allb-a) b-ball a x x |
x x Ixlx Pix x x |
x x x Se | Se x
t BY L. D. PRYOR AND L. H. BRYANT. — 59
TABLE 2.—Continued. Oil Constituents (Except Cymene and Pinenes) of cinerea, Macarthuri and Hybrids.—Continued.
Fluo- Geranyl Eudes- Sesqui- rescent — No. Acetate. | Geraniol. Cineole. | Eudesmol. mene. terpene. Com- ponent. 1 x 3 38 x x SS x KO 3 — _— x x SESE x 36 3K 3K 4 x _ — x 5k BS OK x x x SKK 5 x Xx x _ x 3K »< 3K <x x SK OK 8 = x x x xX XX xX XX x XX 11 = x x x x XX xX X X 36 12 = - <x x xX XX xX XX x XX 13 _— x <x S< 3K ax «XxX K 3K RK 14 32 34 _ xk OK x BS 3< 3K x 3K — 15 _ Dx 3K MK x SS x Xx x Ke OK 16 x 3K = — x 3K x 3K x 3X paex 17 xox x x x 3K x XK x Xx 3 3K OK 18 = x x x XX x xX x XxX Hybrids. 21 _ x 3K x x xxx x SK KX 22 _— =— x x x x xox _ 23 x 3K «KX — 34 3K OK x x — KKK 24 x x Xo KK x x6 OK x 3K OK x OX 25 Not recorded x ORS x KK 36K 26 x ax x 3K OK x6 3K 3K 3K ex x de 27 x x 3K XK x 3 x a <e 29 — x xe x KK KX xx 32 _ x x SKK x x XK SKK OK x SE 33 XK OK x x 3 3K S< x ae 363K SE 34 oS 3K SK _ KK 4 34 x 35 _ ax x x x6 Sax XK x 3K 36 — x aex >aex 36 36 OK x eX ox 38 — - dK OK OK 32K xX xX 34K
#. Macarthuri oils, is present but in still smaller quantities in only 25% of the E. cinerea parent oils and in 60% of the hybrids. In 22% of the hybrids it is present in greater quantity than in any of the parent H. Macarthuri oils.
The sesquiterpene alcohol, eudesmol, which is present to the extent of about 15% in all the parent E. Macarthuri oils, is largely absent from the EZ. cinerea parents but. is present in all the hybrids, sometimes in quantities as large as the EH. Macarthurt parents. Eudesmene, though present, in small amounts in all the oils of the EH. Macarthuri parents, is ‘present at the most as a trace in the E. cinerea parent but present in all the hybrids, over 50% showing considerable amounts.
The unidentified. sesquiterpene is present in almost all oils. It is in greater amount in Z#. cinerea than in E. Macarthuri and still greater than either in the hybrids. The fluorescent compound is present in about half the oils of both parents, whilst in the hybrids 93% contain larger individual amounts than either of the parents.
With regard to the specific gravity, refractive index and optical rotation of the oils, the parents show relative uniformity within themselves, but the hybrids display wide variation in these properties. In this respect hybrid 29 with its low specific gravity and high laevo-rotation’is of interest. This could be due to the presence of substantial. quantities of l-pinene but was not further investigated. The means of the physico-chemical constants of the hybrids lie between those of the parents excepting in the case of the refractive index (Fig. 4). This is explained by the larger quantities of sesquiterpene present in the hybrid oils.
It is clear from these data that recombination of oil constituents is a feature of the hybrids of this cross. Gershtein (1951) studied the oils of a number of Eucalypts and their hybrids. The only chemical constituent assessed was cineole which did not vary greatly in parents or hybrids. The physico-chemical constants published by him, however, indicate that the hybrids contain similar constituents to those found. in the parents. Mirov (1932) in Pinus turpentines has described a P. ponderosa x P.
60 INHERITANCE OF OIL CHARACTERS IN EUCALYPTUS,
i
&
NY
: i
a S
g 8
:
Ss N RY ~“ :
' Vein Angle b Yein Angle 2a 2 é £, paucttlora - £.aves £.peucthora ~ &.Robertsoni e o e 6
Fig. 2a.—Intermediate position of the hybrids in yield in relation to vein angle is illustrated, although there is a preponderance in the progeny of individuals which are identical with the #. pauciflora parent and none actually quite reaches the range of the E. dives parent.
Fig. 2b.—E. pauciflora x E. Robertsoni. Hybrids are indicated by x. Again many of the hybrid individuals are intermediate, but some are identical with either parent. It will be noticed, however, that the recombinants occur in one way only, an individual with a low vein angle sometimes has a high oil yield instead of the normal low yield characteristic of the HE. pauciflora parent, but the reverse, i.e. a high vein angle and low oil yield, does not appear in the material examined.
elective dex
Spectlic gravity
S S “3 = ® 3 J Lop. +18. of Leak x x 3 £.Matdent - £. rubids g g S : . y 8. x = Hybrid
Fig. 3.—The Fi hybrid H. Maideni x EH. rubida is compared with the “pure” parents in oil yield. It is clear that the F1’s are entirely in this respect identical with the H. Maideni parent.
Fig. 4.—The means of various physico-chemical characters of the H. Macarthuri x E. cinerea oils and the hybrids. Three separate conditions are illustrated and in yield the hybrids are almost identical with the low-yielding parent. In specific gravity and leaf shape the hybrids are approximately intermediate between the parents. In refractive index and optical rotation the characters of the hybrids taken as a group considerably exceed those of either of the parents.
BY L. D. PRYOR AND L. H. BRYANT. 61
Jeffreyi hybrid containing terpenes inherited from the ponderosa parent and heptane from the Jeffreyi parent. Work by Snegirev (1936) on Fl and F2 hybrids of two species of Ocimum shows a similar situation in inheritance of oil constituents in the Fl hybrids. However, F2 hybrids in this case on the basis of specific gravity, refractive index and optical rotation data he considered showed “that the composition of the oil in these hybrids had undergone profound changes’’.
49/102
pueda
180 166 193 191 190 188 182
49/203
279 (
224 204 219 2i. 49/201 254 19 49/806 222
Fig. 5.—Typical examples of the leaf venation of the parents are shown: No. 254, #H. pauciflora; No. 279, H. dives; and No. 119, EH. Robertsoni. All are intermediate leaves taken from trees of the same age on about the third pair of leaves on a shoot about four feet from the ground. No. 49/102 indicates the range of venation pattern in the hybrid progeny, H. paucifiora x H. Robertsoni, and No. 49/203 in H#. pauciflora x EH. dives.
5
205
Although no evidence of new compounds (i.e. compounds not present in the parents) was found in the oils of the hybrids, H. cinerea x EH. Macarthuri, the considerable increase in the content of eudesmene, unidentified sesquiterpene and fluorescent component is of interest, since they exceed substantially the amounts of these materials present in either parent.
#. pauciflora x E. Robertsoni and EL. paucifiora x H. dives.
No analysis has been made of the oil components in these combinations, but they afford a good opportunity to examine the inheritance of oil yield in relation to morphological characters. Figure 2 shows the leaf character which has been compared with oil yield, and the various yields obtained with the assessment of the vein angle
62 INHERITANCE OF OTL CHARACTERS IN EUCALYPTUS,
of the different individuals (Fig. 5). In the progenies 49/104 and 49/102 there is very distinct segregation, and a wide range of variation between the two parents, and the same is true of 49/203 in relation to H. dives. Unlike the previous hybrid combination the character, oil yield, segregates and recombines freely. In each hybrid progeny there are some individuals of the same order as either parent with a full range of intermediates. There is also distinct recombination between the character of leaf vein angle and oil yield, as illustrated by Figure 2.
TABLE 3. Component Outer Just in : Fluorescent Sesqui- Inner Component Front of Sample. Cineole. Eudesmol. | Component. terpene Sesqui- Just Behind Inner ( Eudesmene. terpene. Eudesmol. Sesqui- : 3 terpene. =: 2 (Sa ial |; ee ae fem a aT MXM Self 267 | xxxx [<i = x x x x MxM BO || 8M SEK SK «6 il — x x x x MxM 302 xX XX X xX X = x x x ox MxM 303 xx XX x Xx = x x x x MxM 304 xX XX XOX _ x x x x Mx R (F1) 297 KK OK x — x x x x MxR . 298 x KK IK — x x x x MxR 299 SoS OS 3S x — Xx x x x MxR 300 xX X X X = x x xX x x MxR 264 x XxX = x x x x RxR 309 xa <x <4 x 3K KK x 3< Daas RxR 310 x XX <x ax x x< ax x RxR 313 xX Xx eax X< SEK 3K <x x RxR 311 x XX x x x X al. oo XX X . *& x RxR 312 x xX xX x x a oe “KK ees x
Note.—All oils examined gave fluorescence in P. cymene zone of similar intensity. This component would be expected to be present. Pinene is probably also present in all species, but its Rf being similar to that of the outer sesquiterpene (eudesmene) results in cortfusion with this.component on reacting with conc. H.SQ,.
M=Maideni. R=rubida. if ye F1 Hybrids. We \ /
The hybrid studied principally in relation to the parents is H. Maideni x E. rubida. The oil constituents in the’ parénts are rather similar. Quantitatively, however, EH. rubida is a very low yielding species giving about 0:1% oil, whereas H. Maideni is reasonably high, giving about 1:-4% oil. The various components of the oil have been assessed chromatographically, as shown in Table 3. The most striking differences exist in the “fluorescent component”, the sesquiterpene and the component “near eudesmol’’. In the case of the fluorescent component and the component near eudesmol, the Fl hybrid is like the #. Maideni parent. In the case of the sesquiterpene, it appears to be intermediate, although the data are not fully consistent. There are no differences between the cineol and eudesmol contents in the parents and none in the hybrid. A similar examination has been made of FH. cinerea x EH. Blakelyi F1 hybrids, but the differences between the parents are not sufficiently striking to derive any conclusions from the limited material available. In the H. Maideni x EH. rubida the same kind of inheritance pattern is displayed with regard to yield as in the E. cinerea x H. Macarthuri combination, but on this occasion it is reversed, and in the Fl the yield is identical with that of the high yielding parent (Fig. 3). Gershtein’s (1951) figures for the Fl EH. Maideni x EH. viminalis show a similar position. At the same time there is a tendency for the constitution of the H. Maideni parent to be followed in the oil combinations; this suggests that the determinants of the yield and certain of the constituents derived from H#. Maideni in this F1 hybrid are displaying dominance, perhaps like the determinant of the red pigment of the Rutgers tomato (Tomes ef dl., 1952).
BY L. D. PRYOR AND L. H. BRYANT. 63
Discussion.
While the material available does not permit an exhaustive analysis of the pattern of inheritance, it indicates some interesting aspects. It seems that the yield may be determined by one parent in a very far-reaching way, as is shown by the E. cinerea x HE. Macarthuri segregating populations and also in the #. Maideni x EH. rubida F1 hybrid. The same may be true of some of the different components, as is indicated in the fluorescent component in the H. Maideni x H. rubida F1. On the other hand, in some combinations, as the #. paucifiora x H. Robertsoni and E. paucifiora x EL. dives, there is very distinct segregation and recombination of yield, as there is also for geranyl acetate in the H. Macarthuri x E. cinerea combination. In the EH. cinerea x H. Macarthuri and the #H. pauciflora x H. Robertsoni and EL. pauciflora x EH. dives there is evidence of recombination of various characters. In the first place it is between oil constituent and leaf shape, and in the second place between yield and angle of leaf vein. The morphological characters within these combinations have been selected for ease of measurement. There are several characters less easy to measure, as for example leaf thickness in the H. pauciflora x LE. Robertsoni combination, which by inspection seem to follow the same pattern.
A characteristic of segregating progeny derived from hybrids is that the variance of both morphological and oil characters is much greater than that of the parent species. If the facts disclosed so far have a more general application, they suggest that a recombinant between high yield and desirable oil constituents may be found if suitable segregating populations are produced.
The pattern of variation assessed by Willis et al. (1951) in the progeny from presumed forms of E#. maculata shows close analogy with the segregating hybrid populations described above. It is suggested that the origin of these variants is by hybridization between #H. citriodora and E. maculata. The most closely occurring H. citriodora trees, which in this case could be one parent, are believed to be about 40 miles distant from the above forms which occur in a H. maculata stand. Isolated hybrid individuals have been found at this and greater distances and may arise either from long-range outerossing, for example by birds, or as the result of species population movements associated with climatic change. it is not difficult to imagine the origin of such individuals if they are hybrid, and it is suggested, therefore, that this is the explanation for them.
Conclusions.
It is clear that oil characters, both in yield and make-up, are strongly inherited in Hucalyptus, although the determination of the precise pattern will need a good deal more study. So long as evidence is still lacking that Hucalyptus oil is either an attractant: or repellent to insects the function of oil in this regard can only be presumed. From the point of view of the Hucalyptus oil industry, three main lines for developing improved forms are clearly indicated. First and most obviously is the raising of plants from seed from selected stands with known desirable oil characters, as already initiated by Willis; secondly, raising segregating populations from selected naturally-occurring F1 hybrids with a view to obtaining superior recombinants; thirdly, producing experimentally F1 hybrids between parents which have separate desirable characters which, if combined together, would give individuals superior to either parent. It is of particular interest that in some combinations the oils display characters which transcend in magnitude those of either of the parents. This suggests that the biochemical processes resulting in oil formation may be, as in other plants, subject to separate genetic control at each of a number of steps, and that at times in hybrids some steps may be characteristic of one parent leading to the formation of a precursor which is then subject to genetically determined influences derived from the other parent somewhat in the manner suggested for the carotenoid pigment system of tomato (Tomes et al., 1952). Such a process could lead to the formation of compounds in greater quantity than those present in either parent species or even to compounds present in neither. Very much more study and experiment would be necessary to predict reasonably when and how this sort of change would occur.
64 INHERITANCE OF OIL CHARACTERS IN EUCALYPTUS.
However, the likelihood that it is present offers very considerable possibilities in a breeding programme for improved oil production.
It suggests considerable flexibility in evolutionary aspects in the genus if oil is significant in this regard.
Acknowledgements. The generous provision of facilities to make the initial distillations by Professor A. H. Ennor, of the John Curtin School of Medical Research, Australian National University, is greatly appreciated, and sincere thanks are due to Mr. O. Ruzicka for preparing the drawings.
References. '
BAKER, R. T., and SmiTH, H. G., 1920.—A Research on the Eucalypts especialiy in regard to their Essential Oils. Sydney, Government Printer.
BARBER, H. N., 1955.—The Natural History of Natural Selection. Awust. Jowr. Sci., A.N.Z.A.A.S. Report, 3, Section M.
Bryant, L. H., 1950.—Technical Notes, For. Comm. N.S.W., Div. of Wood Technology, Vol. 4 (Special Issue): 6-10.
—, 1955.—Circular Chromatecgraphy of Terpenes