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 entire, it may be undulate or wavy (Fig. 92), serrate or saw-toothed (Fig. 105), dentate or more coarsely notched (Fig. 95), crenate or round-toothed, lobed, and the like. Give examples.

Leaves often differ greatly in form on the same plant. Observe the different shapes of leaves on the young growths of mulberries (Fig. 2) and wild grapes; also on vigorous squash and pumpkin vines. In some cases there may be simple and compound leaves on the same plant. This is marked in the so-called Boston ivy or ampelopsis (Fig. 109), a vine that is used to cover brick and stone buildings. Different degrees of compounding, even in the same leaf, may often be found in honey locust and Kentucky coffee tree. Remarkable differences in forms are seen by comparing seed-leaves with mature leaves of any plant (Fig. 30).

The Leaf and its Environment.—The form and shape of the leaf often have direct relation to the ''place in which the leaf grows. Floating leaves are usually expanded and flat'', and the petiole varies in length with the depth of the water. Submerged leaves are usually linear or thread-like, or are cut into very narrow divisions: thereby more surface is exposed, and possibly the leaves are less injured by moving water. Compare the sizes of the leaves on the ends of branches with those at the base of the