56 NATURE STUDY AND AGRICULTURE 
helps to make its leaf different from the leaves of other 
species. 
Form and Size. — The shape of leaves varies from that 
of the needles of the pine and the narrow blade of grass to the 
circular leaf of a water lily and garden nasturtium, with an 
infinite number of intermediate gradations. A few of the 
typical forms are shown in the accompanying figures. Stu- 
dents of botany sometimes learn the names of a large num- 
ber of these shapes, but that is not necessary for our purpose. 
LEAVES 
Indian corn, showing parallel veins. Basswood, showing netted veins. 
We merely wish to urge the reader to observe the shape and 
size of the leaves carefully so that the mental picture thus 
formed may aid him in distinguishing one plant from another. 
The Margin of the Leaf. — This may be an even line, or 
it may be toothed, or wavy; there may be deep notches or 
indentations that cut the leaf into great lobes, or these notches 
may extend clear down to the midrib and make those lobes 
look like separate leaves. In the last case we have 
Compound Leaves. — In these, the blade of the leaf has 
several entirely separate parts, each joined to the main leaf- 
