148 K. H. CAMBAGE. 



thus showing that the central pinna is not a true prolong- 

 ation of the leaf axis. In such cases the internode between 

 the terminal pair of pinnae and the third or lowest pinna is 

 remarkably short, and one pinna, the fellow to the lowest,, 

 has not developed. What may perhaps be regarded as a 

 strictly tripinnate leaf, however, has recently been found 

 on a seedling of Acacia rigens, where the central pinna of 

 a No. 3 leaf appears to be a prolongation of the main leaf 

 axis, and no trace of the terminal seta can be seen. At 

 the same time the central pinna is not a straight prolong- 

 ation of the common petiole, but bends to the right. The 

 common petiole does not taper gradually into the petiole 

 of the central pinna, but becomes suddenly reduced in size 

 at the point of contact, the thickness of the former being 

 quite double that of the latter, and the leaf looks very like 

 an apparent but not a true tripinnate leaf. (Tiiis Journal, 

 li, 393). 



A second type of tripinnate leaf was noticed as the 

 second leaf of A, stenophylla. (See Plate X, No. 8.) In 

 this instance the basal pair of leaflets appear to have 

 developed into a pair of pinnae; what might have been the 

 midrib of the leaflet in each case became transformed into 

 the rachis of a pinna, thus making the leaf tripinnate, the 

 central pinna having four pairs of leaflets. 



A similar feature is shown in Part V, fig. 3, (This Journ. 

 Vol. lilt, 145), where the basal leaflets on a leaf of a seed- 

 ling of A. podalyricefolia are shown to have developed as 

 a pair of pinnae ; the remainder of the leaf, however, con- 

 sists of a single pair of leaflets only. An exactly similar 

 occurrence to the last has been noted on a third leaf of 

 A. difformis. The first or simply pinnate leaf of a seedling 

 of A. floribunda commonly has two pairs of leaflets, but in 

 one instance one of the basal leaflets developed as a com- 

 plete pinna with two pairs of leaflets. This is the only 

 case I have seen of a divided leaflet on a first leaf. 



