"s differ from s in the principles of their construction and growth. If we examine the base of a leaf-stalk of a tree we shall find a bud there, which, if left alone, will produce a branch or a cluster of fruit the next season. There are no such buds in the axils of fern leaves, not even in those of the , which is peculiarly tree-like in its growth. The growth of a fern is a sort of perpetual lengthening out at both ends. The upward growth, which is more frequently the subject of observation than the growth of the roots, consists first in a process of unrolling, and then of expansion and maturation of the leaves and stems. Because of these and other characters which obviously and without reference to the peculiar nature of their fruit distinguish them from flowering plants, the several parts of a fern are named differently to the corresponding parts in flowering plants. Thus, the true stem or root-stock of a fern is called a ', the true leaf is called a ', the stem which bears the leaf is called the ', and the ramifications of the stipes through the leafy portion corresponding to the leaf-stalks of other plants bears the name of '."