332 THE YOUNG SPOROPHYTE 



strictly dioecious, producing small antheridial or male gameto- 

 phytes and larger archegonial or female gametophytes. Small 

 male gametophytes occur not uncommonly among any of the 

 genera, owing doubtless to their poorer nourishment. The 

 sexual organs are developed upon the under side of the gameto- 

 phyte (Fig. 228, C), probably because this position is of advantage 

 in keeping them in contact with any water that may fall upon the 

 earth [^and thus preventing their drying out. The antheridia 

 develop before the archegonia, often appearing while the gameto- 

 phyte is quite small. They usually project from the surface of 

 the thallus as spherical bodies covered with a single layer of 

 chlorophyll-bearing cells which inclose usually from thirty-two 

 to sixty-four gamete-bearing cells (Fig. 229, A). The male 

 gametes are discharged as in the Bryophyta — the swelling of the 

 antheridium causes the rupture or throwing off of the apical cell 

 and the extrusion of the inner cells as a mucilaginous mass. The 

 gametes are large spirally-coiled bodies provided with numerous 

 cilia and the larger posterior coils enclose a delicate sac containing 

 the remains of the nourishment stored in the mother cell (Fig. 

 229, B). The archegonia are developed on the older prothallia, 

 usually just back of the growing point (Fig. 228, C). The neck 

 of the archegonia, consisting of four rows of cells, projects from 

 the under surface of the prothallium and is usually curved back 

 from the growing point, while the basal portion containing the 

 female gamete remains buried in the tissues of the prothallium 

 (Fig. 229, C). When the female gamete is mature the canal 

 cells become mucilaginous and the lip cells open as in the arche- 

 gonium in the mosses. 



(c) Germination of the Gametospore. — The gametospore ger- 

 minates in a week or more after fertilization, usually dividing very 

 regularly first by a vertical and later by a transverse division into 

 four cells. Each of these cells forms a primary organ of the young 

 sporophyte. Of the two outer cells, the one near to the grow- 

 ing point of the prothallium (Fig. 230, A,c)hy repeated divisions 

 produces the first leaf or cotyledon, while the other one forms 

 the first root (Fig. 230, A, r). Of the two lower cells, the one 

 directly below the leaf cell gives rise to the stem (Fig. 230, A , s) 



