president's address. 43 



met with one instauce of it in the leaf of a sucker. 1 have had the opportunity 

 of looking over several thousand wild seedling-s, representing: about twelve species, 

 in the hope of finding anomalies, but with little sueeess. I have not yet seen u 

 leaf of any Aoacia. seedling or adult, which had a complete terminal pinna; but 

 a leafless thread-like representative of its axis, with a terminal seta, is sometime* 

 to be found in the leaves of reversion-shoots (PL iii., figs 5. 6; PI. viii.. figs. 5-6). 

 1 have also one bipinnate leaf of a seedling, of wliich one pinna has a terminal 

 leaflet. J. leprosa is an Australian species, but no other descriptions of seedlings 

 have been published. If the leaves of Preston's two seedlings really represent 

 tripinnate leaves (that is the apical i>air, together with a terminal ]>inna), thev 

 are, as yet, the first to be recorded . 



What I believe to be tlie correct explanation of them is, that they are merely 

 examples like the three shown in ray PI. iii., fig. 3; and PI. viii., figs. 9-10. The 

 first of these is the leaf of a reversion-shoot. I have others like it; and otliei-s 

 with the two pairs complete, but separated by a very short internode. The 

 second is a leaf of a seedling of .1. my rti folia, and the only specimen I have. But 

 Cambage has figured similar leaves of A. huxifolia and A. pycnantha [Acacia 

 Seedling's. Part iii., p. 393] . When the termisal seta is taken account of, there is 

 no dilliculfy in interin-efing them. The third is a leaf of .1. decurreiis, which is 

 comjiarable with the others. 



I have failed to find any e^-idence whatever that the lowest or proximal i)air of 

 leaflets of the first simply pinnate leaf is ever replaced by a pair of strongly 

 developed pinnae, while the rest of the axis runs on simply pinnate, and rather 

 weak in structure. On the contrary, the apical pair of leaflets is replaced by an 

 apical pair of jsmnsp; and there is no replacement at all of the lower leaflets of 

 the first pinnate leaf before the transition of complete euphyllodes in seedlings 

 of many species, though there is in others, as in the Bijiinnatse. Tlierefore, in 

 every leaf, at every stage -of development, whatex'er else may be present or absent, 

 the apical pair is normally present, and, in the very early stages, it is the only 

 pair. The succession of the pinnae in the development of the bijiinnate leaf is 

 basipetal. 



The leaf of A. decurretis figured by Preston as '"showing a tendency towards 

 a triple pinnation," that is, "showing clearly the third degree on some of the l)asal 

 leaflets of the jjinnas," is a remarkable Ijut rare aberration. This species is a very 

 common one in the Sydney district, and I have examined many leaves; but T have 

 not succeeded in fuiding specimens of this or any other Acacia which sliow it. 

 But I have collected three leaves of Jacaranda, which have a few of the liasal 

 leaflets of the lowest pinnae exemplifying a tendency toward a triple pinnation. 



But what Preston has to say about the leaves of A. heteroplii/lln, of which 

 he gives illustrations, is very important. Tliis is a si)ecies indigenous t^o the 

 Island of Bourbon and Mauritius, or both of them, T believe; and T cannot liear 

 that it is cultivated in Sydney gardens. It is sometimes mentioned in textbooks, 

 and it appears to be a remarkaljle species, like A. melanoryJon, A. nibida. and 

 ])erhaps some <ithers, all of which are worthy of a detailed study of gradational 

 series of plants of various ages. Preston says — "There was also found a fairly 

 large number of stages [of .4. heterojjJii/na] which lead one to doubt greatly whe- 

 ther in all cases it is the petiole only which is transformed to the phvllode, ana 

 pinnae. They illustrate ^•ery well the inversely projiortional ratio in which the 

 proximal one. The prints which follow may, to be sure, represent mere anomalies, 

 but from their numlier, at least, they cannot but raise in one's mind a certain hesi- 

 tation to consider the existence of a law as to method in any way establislied . 



