361 A COMPOUND EUCALYPTUS HYBRID. By L. D. Pryor. (Plates xiii-xiv.) [Read 26th November, 1952.] Synopsis. The existence of a compound hybrid derived from Eucalyptus Rossii,* E. dives and E. macrorrhyncha is deduced on the basis of a progeny test. Introduction. Numerous cases of hybrids between well denned Eucalyptus species have been detected in the field and some others have been synthesized under controlled conditions. During field examinations individuals and sometimes hybrid swarms have been examined in which it has been necessary, for a satisfactory explanation, to postulate that more than two species have been concerned in the parentage. Clearer evidence of this has so far been lacking, but an interesting progeny now two years old has disclosed distinct elements of three separate species in the make-up of the parent tree. Progeny Test. Seed was collected from an apparent hybrid at Black Mountain, A.C.T., and about 40 plants were raised in 1949 and planted out in 1950. The plants are now about two feet high and display very clearly the juvenile characters. The parent was assessed, before the progeny test, as a hybrid between E. Rossii and E. dives. No sign of E. macrorrhyncha was sufficiently clear to suppose at that stage that it was present in the hybrid com-bination. At two years of age, however, undoubted E. macrorrhyncha characters have appeared both in indumentum and leaf shape and are easily recognized in the progeny. Some segregates approximate closely in their juvenile form to each of the other presumed parents also. There are in addition various combinations amongst them of the charac-teristic juvenile forms of the three species (PI. xiii, figs. 1, 2, 3). The juvenile characters of the three species happen to be markedly distinct, which makes the material suitable for detection of such inheritance at an early age. E. dives has sessile, ovate-lanceolate, highly glaucous, opposite leaves (PI. xiv, fig. 8) ; E. Rossii has, after two or three preliminary pairs of leaves beyond the cotyledons, alternate, petiolate, narrow-lanceolate grey-green leaves (PI. xiv, fig. 9) ; E. macrorrhyncha likewise has alternate leaves but they are ovate with a distinctively tapered apex. In E. macror-rhyncha they are also petiolate and dull green, and in addition in the earlier stages are well covered with so-called stellate hairs (actually clusters of hairs on protuberances) which is a distinctive feature of the "stringybark" group of species to which E. macror-rhyncha belongs (PI. xiv, fig. 7). All of these characters are strongly displayed in the progeny. Some individuals in the present stage are almost indistinguishable from E. dives (PI. xiii, fig. 5), or alternatively from E. Rossii (PI. xiv, fig. 6). Those approaching E. macrorrhyncha (PI. xiii, fig. 4), however, are less close to the charac-teristic form of that species in the juvenile condition than the former two. Nevertheless the two distinctive characters of "stellate hairs" and leaf shape, as well as the general habit of the seedlings, are unmistakably present, and there is little doubt that E. macror-rhyncha has entered into the combination. Other characters of diagnostic value will appear as the plants flower and fruit and as the mature type of bark develops which will allow more accurate assessment of the degree of contribution from each parent. Nomenclature and spelling-as in Blakely, "A Key to the Eucalypts", 1934.
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