ON LEAVES. 



355 



nate (Fig. 16), and differ in nothing from those characteristics of the 

 genus. In the later ones, however, the leaflets are reduced in number, 

 and the leaf-stalk is slightly compressed laterally. The fifth or sixth 

 leaf, perhaps, will have the leaflets reduced to a single pair, and the 



Fig. 16. 



Fig. 11. 



leaf-stalk still more flattened, while, when the plant is a little older, 

 nothing remains except the flattened petiole. This in shape, as already 

 observed, much resembles a narrow willow-leaf, but flattened laterally, 

 so that it carries its edge upward, and consequently exposes as little 

 surface as possible to the overpowering sun. In some species the long 

 and narrow phyllodes carry this still further by hanging downward, 



Fig. 18. 



Fig. 19. 



and in such cases they often assume a cimeter-like form. This I would 

 venture to suggest may be in consequence of one side being turned out- 

 ward, and therefore under more favorable conditions. 



In one very interesting species {Acacia melanoxylon, Fig. 17), the 



