FIRST READING.
By far the greater number of plants have leaves of an oval shape, and we have only to go through our forests and gardens to see them on every hand. Exceedingly varied are they indeed, from very narrow to very broad oval, some with toothed, some with smooth edges, and some even deeply notched; and yet to such an extent does this tendency toward a rounded form prevail, that there seems scarcely a plant in whose leaves a trace of the oval may not be found.
The apple tree gives us a good specimen of an oval leaf; and an immense number of plants have leaves resembling it in shape. In many plants, the leaves are almost the very counterpart of those of the apple-tree; in some, they are narrower, and in others, still narrower, till we come to very slender blades like those of the grasses; and then, beyond still, to the needle-like leaves of the pines. On the other hand, plants are to be found with leaves broader than the apple-leaf; and so on, rounder and rounder, until we come to such plants as the nasturtium and the water-lily, whose leaves are almost as round as circles.
Leaf of Apple.
There are certainly to be met with most remarkable departures from the oval shape, and we need but refer to such leaves as those of the buckwheat, to find that roundness seems to be entirely absent.
Buckwheat Leaf.
This style of leaf, of which there are many variations, is apparently built on the model of the heart-shaped leaf, of which the morning-glory affords a familiar example. It will be noted, however, that instead of the curvilinear flow of outline, in which a tendency to oval roundness is plainly visible, the hastate leaf of the buckwheat is angular throughout.