32 



MOSSES AND FERNS 



CHAP. 



have, as usual in such cases, decidedly denser contents than the 

 peripheral ones. 



The lower one or two segments and the terminal ones do 

 not take part in the formation of sperm cells, but simply form 



® 



ol 



Fig. s. — A-F, Development of the antheridium of R. glauca, seen in longitudinal 

 section; G, cross-section of a young antheridium of the same; H, antheridium of 

 R. trichocarpa; I, sperm cells of R. glauca. Figs. E, F, Xiso; I, X6oo, the 

 others X300. 



part of the wall of the antheridium. The central cells now 

 divide with great rapidity, the division walls being formed 

 nearly at right angles to each other, so that the central part of 

 the antheridium becomes filled with a very large number of 

 nearly cubical cells. The divisions are formed with such 

 regularity that the boundaries of the original central cells 

 remain very clearly marked until the antheridium is nearly 

 mature. The basal cell of the antheridium rudiment in R. 

 glauca divides once by a horizontal wall (Fig. 5, B, D) and 

 forms the short stalk of the antheridium, which, however, is 

 almost completely sunk in the thallus. Between this stalk 

 and the central group of cells there are usually two layers of 

 cells, so that the wall of the antheridium is double at the base, 

 while it has but a single layer of cells in the other parts. The 



