BRYOPHYTA 



195 



off three primary wall cells from the primary axial cell (Fig. 159A). The 

 axial cell, by a transverse division, gives rise to the cover cell and central 

 cell (Fig. 159B). The development of the axial row is similar to that of 

 the Jiingermanniales. The central cell divides to form the primary neck 

 canal cell and primary ventral cell (Fig. 159C). The neck canal cells, 



B 



F 



Fig. 159. Development of the archegonium of Sphagnum subsecundum. A, formation of 

 primary axial cell; B, fornnation of cover cell and central cell; C, formation of primary neck 

 canal cell and primary ventral cell, the cover cell divided vertically; D, archegonium with 

 primary ventral cell and two neck canal cells; E, later stage with four neck canal cells; F, 

 archegonium with egg, ventral canal cell, and nine neck canal cells; A to E, X525; F, 

 X300. {After Bryan.) 



numbering eight or nine, all arise directly from the primary neck canal 

 cell, while the ventral canal cell and egg, approximately equal in size, are 

 produced by a transverse division of the primary ventral cell (Fig. 

 159D-F). The mature archegonium has a long stalk, a massive venter, 

 and a long twisted neck. 



Sporophyte. The fertilized egg of Sphagnum undergoes a series of 

 transverse divisions that result in the formation of a short filament of six 

 or seven cells (Fig. 160). Vertical walls then appear and the embryo 

 becomes cylindrical. It next becomes differentiated into an upper fertile 



