With all Ferns the production of spores is confined to the leaves. In many instances there is no distinction between the fertile and the barren leaves. The stem does not start at once to produce leaves bearing the sporangia or spore cases. Thus, in the very young Fern the fronds are always barren; as the stem becomes older, fertile fronds are produced. In some cases the sporangia are borne on distinct leaves, as in the case of the Hard Fern, or on special parts of the leaves, in the manner to be seen in the Royal Fern. The difference in such cases is not really a very important distinction. A careful examination of the fertile portion of a Royal Fern frond will show a small amount of green tissue, or mesophyll, as it is called, at the lower portion of the pinnæ. Actually the fertile leaf, or part of a leaf, is similar to the barren portions, save that it produces a much reduced amount of green tissue or, in some cases, perhaps none at all. In general appearance the Club Mosses bear a resemblance to the true Mosses, and hence the popular name, which is certainly rather misleading. With these plants the leaves are small and almost bristle-like, and are gathered closely round the stem. In many of the Club Mosses a large part of the stem lies closely along the ground, and from this at intervals roots are sent down into the soil and leafy shoots rise upwards. The sporangia are produced on special leaves, which are usually gathered together in the form of cones. Although they vary somewhat in size, all the Horsetails are striking plants. Here there is a branching underground rhizome from which arise the aerial stems. The most distinctive feature of the plant are the whorls of smaller branches which arise from the joints of the main stem. These carry on the work which is usually assigned to the foliage of the average plant,—that is, the assimilating of carbon from the carbonic acid of the atmosphere. The real leaves of the Horsetail are much reduced in size, and take very little part in the work of nutrition. We shall find them at the joints of the stem as rings, each collection forming a kind of sheath. The leaves, which are usually of the same number as the branches, show no sign of their individuality, save in the little projecting teeth. In some species the fertile shoots, which appear in the form of cones, are produced specially. These appear in the spring before the ordinary vegetative growths, and are quite destitute of chlorophyll. In other species the normal green shoots are fertile at the termination. The sporangia are borne on curious scale-like leaves, a large number of which go to the making of a cone.