BRYOPHYTA 



201 



When mature, the antheridium ruptures at the apex, the sperms being 

 discharged in a mass. 



The archegonium also develops by means of a dolabrate apical cell, but 

 only a comparatively few segments are cut off (Fig. 165.4). In the ter- 

 minal cell then appear the three characteristic walls that differentiate the 

 primary wall cells from the primary axial cell (Fig. IGoB). A transverse 



-a) 



L^ 



^©' 



Fig. 164. Development of the antheridium of Mnium affine, X400. A, young stage; B, 

 beginning of differentiation of primary spermatogenous cells; C, slightly older stage; D, 

 antheridium showing subdivision of spermatogenous tissue. 



division of the axial cell results in the formation of the cover cell and cen- 

 tral cell, the latter soon giving rise to the primary neck canal cell and 

 primary ventral cell (Fig. 165C, D). Later development is characteristic 

 in that the cover cell cuts off lateral segments that add to the neck cells 

 and inner segments that contribute to the neck canal cells. Thus the 

 upper neck canal cells are derived from the cover cell, the lower ones from 

 the primary neck canal cell, while the ventral canal cell and egg, as 

 usual, arise from the primary ventral cell (Fig. \65E-H). The mature 

 archegonium has a long stalk, a massive venter, and many neck canal 

 cells — sometimes up to 50 or 60. 



Sporophyte. In the Bryales the sporophyte reaches a high degree of 

 specialization. During its early development a large calyptra is formed 



