The leaves in most species are like those of the larger club mosses, but more delicate. They are arranged in four rows on the upper side of the stem, two being larger than the others. The smaller branches grow out sideways so that the whole branch appears flattened, reminding one of the habit of the higher liverworts. Special leafless branches (_B_, _r_) often grow downward from the lower side of the main branches, and on touching the ground develop roots which fork regularly. The sporangia are much like those of the ground pines, and produced singly at the bases of scale leaves arranged in a spike or cone (_A_, _sp._), but two kinds of spores, large and small, are formed. In the species figured the lower sporangium produces four large spores (macrospores); the others, numerous small spores (microspores). Even before the spores are ripe the development of the prothallium begins, and this is significant, as it shows an undoubted relationship between these plants and the lowest of the seed plants, as we shall see when we study that group. If ripe spores can be obtained by sowing them upon moist earth, the young plants will appear in about a month. The microspore (Fig. 74, _K_) produces a prothallium not unlike that of some of the water ferns, there being a single vegetative cell (_x_), and the rest of the prothallium forming a single antheridium. The spermatozoids are excessively small, and resemble those of the bryophytes. The macrospore divides into two cells, a large lower one, and a smaller upper one. The latter gives rise to a flat disc of cells producing a number of small archegonia of simple structure (Fig. 74, _I_, _J_). The lower cell produces later a tissue that serves to nourish the young embryo. The development of the embryo recalls in some particulars that of the seed plants, and this in connection with the peculiarities of the sporangia warrants us in regarding the _Ligulatæ_ as the highest of existing pteridophytes, and to a certain extent connecting them with the lowest of the spermaphytes.