426 



MOSSES AND FERNS 



CHAP. 



ance and size of the male and female plants, and they are 

 not always distinguishable by the naked eye. While in this 

 species, as in others, the antheridia may form at the ends 

 of the prothallial branches, they also may be formed upon 

 a meristem quite like the archegonia, and are usually in 

 this species in groups, so that longitudinal sections show 

 antheridia of very different ages, all evidently derived from the 

 activity of the meristem (Fig. 221). The development shows 

 a close resemblance to that of the eusporangiate Ferns, and 

 in connection with the other points in the growth of the 

 gametophyte and sexual organs, suggest a nearer connection of 

 these two groups than is usually admitted. Here, as in the 



Fig. 221. — Development of the autheridium, X 190. A, Longitudinal section through the antheridia! 

 meristem showing antheridia of different ages ; B, longitudinal section of young antheridium, 

 X375 ; C, two sections of a terminal, single antheridium, nearly ripe, X 190 ; D, three 

 transverse sections of young antheridium, X 190 ; 0, opercular cell. 



eusporangiate Ferns, the antheridium mother cell is divided 

 into an inner and an outer cell, of which the inner one forms at 

 once the sperm cells. When the antheridium arises at the end 

 of a filament, the divisions in the terminal cell are very much 

 like those in Osmunda. In the mother cell three intersecting 

 walls enclose a tetrahedral cell, which then has the cover cell 

 cut off by a periclinal wall. In both forms of antheridium the 

 subsequent history is the same. The central cell divides first 

 by a transverse wall, followed by vertical walls in each cell, and 

 subsequently by numerous divisions which show no definite 

 arrangement (Fig. 221, C), and produce a very large number of 

 sperm cells. In the cover cell only radial walls are formed, and 



