When very young the archegonium is composed of an axial row of three cells, surrounded by a single outer layer of cells, the upper ones forming five or six regular rows, which are somewhat twisted (Fig. 54, _A_, _B_). As it becomes older, the lower part enlarges slightly, the whole looking something like a long-necked flask (_C_, _D_). The centre of the neck is occupied by a single row of cells (canal cells), with more granular contents than the outer cells, the lowest cell of the row being somewhat larger than the others (Fig. 54, _C_, _o_). When nearly ripe, the division walls of the canal cells are absorbed, and the protoplasm of the lowest cell contracts and forms a globular naked cell, the egg cell (_D_, _o_). If a ripe archegonium is placed in water, it soon opens at the top, and the contents of the canal cells are forced out, leaving a clear channel down to the egg cell. If the latter is not fertilized, the inner walls of the neck cells turn brown, and the egg cell dies; but if a spermatozoid penetrates to the egg cell, the latter develops a wall and begins to grow, forming the embryo or young sporogonium. [Illustration: FIG. 55.--Longitudinal section of a nearly full-grown sporogonium of _Madotheca_, which has not, however, broken through the overlying cells, × 25. _sp._ cavity in which the spores are formed. _ar._ abortive archegonium.] The first division wall to be formed in the embryo is transverse, and is followed by vertical ones (Fig. 54, _E_, _em._). As the embryo enlarges, the walls of the basal part of the archegonium grow rapidly, so that the embryo remains enclosed in the archegonium until it is nearly full-grown (Fig. 55). As it increases in size, it becomes differentiated into three parts: a wedge-shaped base or "foot" penetrating downward into the upper part of the plant, and serving to supply the embryo with nourishment; second, a stalk supporting the third part, the capsule or spore-bearing portion of the fruit. The capsule is further differentiated into a wall, which later becomes dark colored, and a central cavity, in which are developed special cells, some of which by further division into four parts produce the spores, while the others, elongating enormously, give rise to special cells, called elaters (Fig. 56, _B_). [Illustration: FIG. 56.--Spore (_A_) and two elaters (_B_) of _Madotheca_, × 300.] The ripe spores are nearly globular, contain chlorophyll and drops of oil, and the outer wall is brown and covered with fine points (Fig. 56, _A_). The elaters are long-pointed cells, having on the inner surface of the wall a single or double dark brown spiral band. These bands are susceptible to changes in moisture, and by their movements probably assist in scattering the spores after the sporogonium opens.