Fig. 50. Simple leaf of the Cherry.
When you go into the woods or gardens to study the leaves, first look at single ones, collecting as many kinds as you can. Though their shape varies very much, you will find that in almost all cases they are green, expanded, and flat. Let us first examine a single simple leaf, like that of a cherry. You will see that the expanded part (called the leaf blade or lamina) narrows down to a small stalk, which connects the blade with the stem from which the leaf is growing; this stalk is called the leaf stalk or petiole. Then at the base of it, just where it joins on to the stem, there are two little leaf-like structures which are not true leaves, but which belong to the leaf and are called stipules; they are attached to the base of the petiole, which spreads out to clasp the stem, and is called the leaf base (see fig. 50). Such a leaf shows us all the parts of a simple leaf; but some leaves have no stalks, others no stipules, and so on.
Fig. 51. Compound leaf of the Rose.
Let us compare a rose leaf with the simple leaf of a cherry, oak, or beech. In the rose you will find five or seven small leaflets arranged on a single main stalk, and each of these leaflets separately is very much like a single leaf of the beech. Such a leaf as this we call compound, for it is divided up into several parts, each of which looks like a whole leaf (see fig. 51).
Leaves are of very many different kinds and shapes, and special names have been given to each kind, which you can look up in a book if you want to classify them.
Fig. 52. Peltate leaves of Nasturtium, showing the stalk attached in the middle of the lamina.