30 



MOSSES AND FERNS 



CHAP. 



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 (i), always into 

 four in R. Bischoffii, and the same seems to be true for R. tricJio- 

 carpa (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 



Fig. 4. — A, Archegonium of Riccia trichocarpa, showing the ventral canal cell (f), 

 XS2s; B, ripe archegonium of R. glauca, longitudinal section, X260. 



separates the ventral canal cell from the Qgg. 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 — Janczewski 

 gives ten in R. BiscJwifii. The basal cell finally divides into a 

 single lower cell whicli remains undivided, completely sunk in 

 the thallus, and an upper cell which divides into a single layer 

 of cells forming part of the venter, and continuous with the 

 other peripheral cells. The mature archegonium (Fig. 4) 



