VI. THE BRYALES 197 



apical cell is divided by a septum parallel with its outer face 

 into an inner cell, which with the inner cells ni the se<(nients 

 forms the mass of sperm cells, and an outer cell which prc^luces 

 the upper part of the wall. Before the full number is com- 

 pleted, the secondary divisions begin, ])roceeding from the base 

 upward. These are very regular, and correspond closely to 

 those in the antheridium of the Jungermanniaceae, and can only 

 be clearly made out by comparing transverse and vertical sec- 

 tions of the young antheridium. Fig. 102, H, shows a diagram 

 illustrating this : i is the wall separating two adjacent seg- 

 ments, and 2 the first wall formed in the segment itself. The 

 wall 2, it will be seen, starts near the middle of the periphery 

 of the segment and strikes the wall i far to one side of the 

 centre, so that the segment is thus divided into two cells of very 

 unequal size, although their peripheral extent is nearly equal. 

 The next wall (3) strikes both the w^all i and 2 at about equal 

 distances from the periphery, and thus each segment is divided 

 into an inner cell wdiich in cross-section has the form of a tri- 

 angle, and two peripheral cells. The latter divide only by 

 radial walls, and give rise to the single-layered wall of the 

 antheridium. The inner cells of the segments by further di- 

 vision in all directions form the mass of sperm cells. The first 

 division w^all in the central cell starts from near the middle of 

 the segment wall and curves slightly, so that the two resulting 

 cells are unequal in size. From this first division wall usually 

 two others having a similar form extend to the peripheral cells, 

 and these are next followed by others nearly at right angles 

 to them. After this transverse and longitudinal walls succeed 

 with such regularity that the limits of the primary segments 

 remain perfectly evident until the antheridium is nearly full 

 grown. 



The central cells in the fresh antheridium are strongly re- 

 fringent and in stained sections show^ a much more granular 

 consistence than the outer ones. The nucleus, as in other cases 

 studied, loses its nucleolus before the formation of the sperma- 

 tozoids begins. The latter in their structure and development 

 correspond with those of Sphagnum, but owing to their smaller 

 size are not favourable for studying the minute details of de- 

 velopment. 



In the peripheral cells are numerous chloroplasts which in 

 the ripe antheridiu.m lie close to the inner w^all of the cell As 



