284 



in nature. The significance of swellings found frequently at the crowai of young Gum 

 trees is not yet understood. They do not appear to be detrimental to the tree." A 

 further note on this crown gall will be found at p. 552 of the work quoled. 



Forest Red Gum {Eucah/ptus iere'.iconus). Fig. 21. Seedlings of 4 to 6 feet were inoculated. Tl;o 

 first succcs.sful inoculation.s were made May 16, 1910. On Jlarch 25, 1912, there was one large knot and 

 one very small one at points of inoculation. September 2, 1911, inoculated a seedling about i inch 

 in diameter. February 20, 1912, there were two small knots. On 5Iarch 2G, 1912, one of these knots 

 had grown rapidly in size, the other had not changed. 



Inoculations were made on small seedlings July 29, 1910, on the branches. Typical roundish knots 

 or galls had developed on September -5, 1910. 



The appearance of a Eucalyptus nodule (or rather a pair of axillary stem-nodules 

 still unfused) may be seen in the figure of one in E. paniculuta, see fig. 12. Plate 57, 

 Part XIII of the present work. 



Fletcher and Musson (p. 198) say : — 



Were It not that, by a fortuitous combination of circumstances, the axillary stem-nodulcs are able 

 to fuse in pairs, the fused pairs to concresce, and the reinforced, composite, stem-encircling tiunours thus 

 enabled to incorporate roots, and so last for some considerable time, or even permanently, both the nodules 

 and any shoots they might develop would be short-lived and abortive, as they actually are in refractory 

 seedlings, and as the shoots on the lower pairs of concrescences also are. . . . 



But in the natural inoculations in the lower axils of the young seedlings of Eucalypts, v/hich furnish 

 some of the most valued hardwood timbers, we are inclined to think that the organisms are confmo.l to the 

 out-growths, and the circling tumours to which they give rise, and probably do not invade the tissues of the 

 seedlings. The tumours do not kill the seedlings, or even seriously damage their tissues. They are a 

 drag on the normal development of the plants, especially so when shoots do not develop, and by interfering 

 -nith the water-supplv, and also by their shoots preventing the development of the normal branching. 

 In the Mallees, so much water is intercepted by the tumours that the seedling-stem is dwarfed; and, by 

 the persistence of the shoots, the growth habit is permanently distorted, so that the plants are prevented 

 from realising their potentialities as trees. The seedling-stem may possibly be sometimes crowded out and 

 got rid of. But the stem-nodules, as well as the composite tumours to which they give rise, .arc complex 

 tumours, composed of both somatic cells and germ cells; and the latter are totipotent, because in the per- 

 .sistent-composite tumours of the Mallees, the tumour-shoots complete their growth, flower and fruit, and 

 produce seed. Even in the non-Mallees, if the seedling-stem is lost, two tumour-shoots may take its place, 

 attain to tree-size, and flower and fruit. But they do not prematurely disclose their embryonic possibilities 

 in the way that some of Erwin Smith's artificially-produced monstrosities did. Also, the production of 

 these tumours in Eucalyptus under natural conditions is a matter of long standing. The Mallee scrubs, 

 which must have been the development of centuries, were in their ])rime when civilised man first saw them, 

 nearly 101 years ago. 



Tlien follow a number of interesting references to Mallees, arranged in chrono- 

 logical order, particularly as regards the " root " — ^the " Mallee-roots " which form 

 an important portion of the fuel supply in South Australia and those portions of 

 Victoria and New South Wales adjacent thereto. 



The authors (pp. 204, 228) state that they have met with six species of Eucalypts 

 exempt from tumours or stem-nodules, viz., E. oreades R. T. Baker, E. pilularis Sm.,. 

 E. sp. (from foot of Blue Mountains, New South Wales, on the western side), E. fiigantea 

 Hooker, E. regnans F.v.M. var. fastigata. I hope the paper wll direct the attention 

 of Australians to phenomena which have only been imperfectly studied as regards 



