30 . prksiijkxt'.s aui)1;k.>s. 



flattened leaf-axes lor pairs of jiiuuie, irom the nature ot the case, the suhstitu- 

 tion or ruplaeeuient caiiuot take place iustautaneously in a flash, but only by 

 gradual, intermediate stages. It necessarily follows, therefore, that some indi- 

 cation of both can and may be present at the same time, but in an invei-sely pro- 

 portional ratio. If the pinnse are strongly in evidence, after the struggle be- 

 gins, the euphyllode will be only slightly indicated; wiiereas if the euphylloiie 

 is strongly in the ascendant, but not yet complete, the pinnas will show signs 

 of some kind ur other that they are on the wane. Tiie swamping, euphyllode- 

 producing tendency usually acts too promptly in young seedlings to show the 

 inversely proportional relations between the two contestants very satisfactorily. 

 But good examples of reversion-foliage, and the leaves of reversion-shoots sliow 

 them most beautifully and convincingly. 



Sir Jolin Lubbock, afterwards Lord Avebiuy, in his great book "On Seed- 

 lings" (18i)2), mentions or describes, or describes and figures seedlings of se\en 

 species of Acacia. But his material was very limited, and sometimes lestricted 

 to a single seedling. It is remarkable that the species, whose seeds he was able 

 to get, are all out-of-the-way or inland species, and do not include a single 

 example of our common and familiar species. Lubbock was interested in them 

 as seedliug-s merely; and it was not his object to discuss the nature of the euphy- 

 lodes of those that were euphyllodineous species. Having complete seedlings at 

 his disposal, he was able to recognise, this time, that the flrst of six of them was 

 an abrujitly pinnate leaf. But of two species, not tigured, A. Oswaldi and A. 

 aeanthocarpa he says — ''Leaves compound and abruptly pinnate or reduced to 

 phyllodes," and "First leaves compound, abniptly pinnate"; but as he makes no 

 mention of the presence of bipinnate lea\es in either case, one does not know 

 how to take these statements, since his descriptions of the seedling's of these two 

 species are all that are available at present. On the other hand, he describes I he 

 flrst six leaves of a seedling of A. Burkitti as bipinnate. This is the oidy 

 Acacia-seedling, without an abruptly pinnate flrst leaf, or a pair of them, yet 

 recorded. Lubl)o(k also recognises the presence of Hentiiam's terminal seta in 

 the seedlings of two species, but unfortunately he locates it on the petioles. 

 Thus, of the flrst six leaves of .^1. Burkitti, all bipinnate with one pair of pinn;e, 

 he says "petiole excurrent between the pinn;e, with a subulate slender point." 

 Also of A. vertieillata he say.s — "Leaves at flrst pinnate then bipinnate, then 

 reduced to phyllodes . . . petioles laterally compressed . . . and ]>ni- 

 jecting beyond the pinnw with a subulate acute aristate point." The petiole of a 

 comjxiund leaf is tiie portion of the common petiole, or primary leaf-axis, below 

 the lowest pair of piniia»; therefore, all the ])inna3 are attached to the rhachis; 

 consequently it is the common petiole, or its distal couipcment, the rhachis, which 

 terminates in an excurrent point or terminal seta. If the petiole terminates in an 

 "excurrent i)oint," then, since the latter is above the pair of pinnw. these nuist 

 be attached to the petiole — whidi is absurd. He correctly adds, however — • 

 "rhachis of pinna- excurrent in the form of a small subulate point." And lie 

 sliould have said — common petiole, or the rliachis which is its distal component, 

 with an excurrent point. But, accepting the current idea, tliat the phyllodes of 

 Acacias are simply flattened petioles, he tacitly assumed and took for granted, 

 as he did in the earlier passage quoted above, that the single pair of pinnae of 

 his bipinnate leaves was the lowest or basal pair, whereas it is the apical or 

 uppermost pair which appears first; and that the stalk to which the pinnffi were 

 aflaclied was the petiole, whereas it was the common i>etioh> or primary leaf- 

 axis, as is proved by its lerminating in an excurrent point or terminal seta. 



