Page:Popular Science Monthly Volume 27.djvu/371

Rh (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



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,



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 outward, and therefore under more favorable conditions.

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