32 



MOSSES AND FERNS 



CHAP. 



Almost coincident with the first cell division in the 

 archegonium rudiment there is a rapid growth of the cells 

 immediately surrounding it. These grow up as a sort of ring 

 or ridge about the archegonium, which is thus gradually 

 immersed in a cup-shaped cavity, and the growth of the cells 

 about this keeps pace with the increase in length of the 

 archegonium, so that even when fully grown only the very 

 extremity of the neck projects above the level of the thallus. 

 The whole process is undoubtedly but a modification of the 



c 



A. 



Fig. 5. — A-F, Development of the antheridium of K. glauca, seen in longitudinal section ; G, cross- 

 section of a young antheridium of the same ; H, antheridium of R. hirta ; I, sperm cells of R. 

 g-lauca. Figs. E, F, X 150 ; I, x6oo, the others X300. 



ordinary growth of the dorsal part of the thallus, and the 

 space about the archegonium is the direct equivalent of the 

 ordinary air-spaces. 



The first division in the primary antheridial cell is the 

 same as in the archegonium, but the later divisions differ much 

 and dp not show such absolute uniformity. The first division 

 wall in the upper cell (Fig. 5, B) is always transverse, and 

 this is followed by a second similar wall, but the subsequent 

 divisions show considerable variation even in the same species. 

 After a varying number of transverse walls have been formed. 



