LEAVES — FORM AND POSITION 



8i 



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 Hke. 

 Give examples. 



Leaves on the same ])lant often diffei' greatly in form. 

 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 ampelop- 

 3is (Fig. 109), a vine 

 ihat is used to cover 

 brick and stone build- 

 ings. Different degrees 

 of compounding, even 

 in the same leaf, may 

 often be found in honey 

 locust. Remarkable dii- 

 ferences 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 grozvs. 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 



Fig, 109. — Different Forms of Leaves 

 FROM ONE Plant of Ampelopsis. 



