30 MOSSES AND FERNS chap. 



an inner one. The latter divides but a few times and forms 

 the short stalk ; the outer cell, which has dense granular 

 contents, develops into the archegonium or antheridium as the 

 case may be. In the former case the divisions follow the 

 order already indicated for the typical Liverwort archegonium. 

 In the outer cell, which continues to enlarge rapidly, a nearly 

 vertical wall is formed (Fig. 2, C), which divides the cell into 

 two very unequal parts. This wall is curved and strikes the 

 periphery of the mother cell at about opposite points (Fig. 2, 

 G, l). A second wall of similar form is next formed in the 

 larger cell (G, 2), one end of which intersects the first wall, 

 and finally a third wall (3) intersecting both of the others is 

 formed. The young archegonium seen in vertical section at 

 this stage (Fig. 2, D) shows a large central cell bounded by 

 two smaller lateral ones ; in cross -section the central one 

 appears triangular. Each of the four cells of which the 

 archegonium rudiment is now composed divides into two. 

 The outer ones each divide by radial walls into equal parts, 

 and the central one divides into an upper smaller cell (cover 

 cell) and a lower larger one (Fig. 3, E). The next divisions 

 are horizontal and divide the young archegonium into two 

 tiers of cells. The lower one forms the venter, and the upper 

 one the neck, and next the cover cell divides into four nearly 

 equal cells by intersecting vertical walls. The archegonium at 

 this stage (Fig. 2, F) is somewhat pear-shaped, being smaller 

 at the bottom than at the top, and the basal cell is still 

 undivided. It now rapidly increases in length by the trans- 

 verse division and growth of all its cells, and there is at the 

 same time a marked increase in diameter in the venter, which 

 finally becomes almost globular (Fig. 4). The axial cell of 

 the neck, the neck canal cell, divides, according to Janczewski,^ 

 always into four in R. Bischoffii, and the same seems to be true 

 for R. hirta (Fig. 4, A), and probably is the same in other 

 species. The number of divisions in the outer neck cells is 

 various, but is most active in the lower part, but in the central 

 cell of the venter there is always but a single transverse 

 division which separates the ventral canal cell from the &'g^. 

 The four primary cover cells enlarge a good deal as the 

 archegonium approaches maturity, and divide by radial walls 

 usually once, so that the complete number is normally eight — 



^ Janczevvski (i). 



