Let us just notice a few of the types. The cherry, beech, and others which are simple with slightly pointed ends, we may call by the proper term ovate. Then there are leaves like those of the nasturtium, where the leaf blade is circular and the leaf stalk does not come in at the base of the leaf, but is attached to the middle of it; such leaves as that are called peltate.
The broad or rounded leaves, which spread out like the palm of a hand, such as the ivy (see fig. 26), are called cordate or lobed, and when compound, as are those of the horse chestnut, palmate.
Fig. 53. Needle leaves of Pine growing in pairs.
All the grasses and the many plants belonging to their family have very long, narrow leaves, which we call linear, while those of the pine trees are sharp and pointed, and are called needle leaves.
Fig. 54. Seedling of Rose; (c) cotyledons; (a) next leaf, simple, but toothed; (b) next older leaf divided into three leaflets.
As we noticed in comparing the leaves of the rose and cherry, some plants have very much more complicated leaves than others. Now such complicated structures do not develop on a plant all at once, as you can see if you examine a very young rose seedling. The first pair of leaves or cotyledons do not remain inside the seed as they do in the bean, but grow outside into the air and become green; they are quite simple leaves with smooth edges. The next leaf which unfolds is also simple, but it has a deeply toothed edge (see fig. 54), while the leaf following that is a compound leaf, divided into three leaflets. The other leaves gradually get five and then seven leaflets as the seedling grows up.