When ripe, the upper part of the oögonium dissolves, allowing the eight cells, still enclosed in a delicate membrane, to escape (Fig. 27, _H_). Finally, the walls separating the inner cells of the oögonium become also absorbed, as well as the surrounding membrane, and the eight egg cells escape into the water (Fig. 27, _I_) as naked balls of protoplasm, in which a central nucleus may be dimly seen. The antheridia (Fig. 26, _F_, _G_) are small oblong cells, at first colorless, but when ripe containing numerous glistening, reddish brown dots, each of which is part of a spermatozoid. When ripe, the contents of the antheridium are forced out into the water (_G_), leaving the empty outer wall behind, but still surrounded by a thin membrane. After a few minutes this membrane is dissolved, and the spermatozoids are set free. These (Fig. 27, _K_) are oval in form, with two long cilia attached to the side where the brown speck, seen while still within the antheridium, is conspicuous. The act of fertilization may be easily observed by laying fresh antheridia into a drop of water containing recently discharged egg cells. To obtain these, all that is necessary is to allow freshly gathered plants to remain in the air until they are somewhat dry, when the ripe sexual cells will be discharged from the openings of the conceptacles, exuding as little drops, those with antheridia being orange-yellow; the masses of oögonia, olive. Within a few minutes after putting the oögonia into water, the egg cells may be seen to escape into the water, when some of the antheridia may be added. The spermatozoids will be quickly discharged, and collect immediately in great numbers about the egg cells, to which they apply themselves closely, often setting them in rotation by the movements of their cilia, and presenting a most extraordinary spectacle (_J_). Owing to the small size of the spermatozoids, and the opacity of the eggs, it is impossible to see whether more than one spermatozoid penetrates it; but from what is known in other cases it is not likely. The egg now secretes a wall about itself, and within a short time begins to grow. It becomes pear-shaped, the narrow portion becoming attached to the parent plant or to some other object by means of rootlets, and the upper part grows into the body of the young plant (Fig. 27, _M_). [Illustration: FIG. 27.--_H_, the eight egg cells still surrounded by the inner membrane of the oögonium. _I_, the egg cells escaping into the water. _J_, a single egg cell surrounded by spermatozoids. _K_, mass of spermatozoids surrounded by the inner membrane of the antheridium. _L_, spermatozoids. _M_, young plant. _r_, the roots. _K_, × 300; _L_, × 600; the others, × 150.]