vir THE BRYINEAL 189 



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

 into an inner cell, which with the inner cells of the segments 

 forms the mass of sperm cells, and an outer cell which produces 

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

 pleted, the secondary divisions begin, proceeding 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 verti- 

 cal sections of the young antheridium. Fig. 90, H shows a 

 diagram illustrating this : i is the wall separating two adja- 

 cent segments, 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 wall i and 2 at 

 about equal distances from the periphery, and thus each 

 segment is divided into an inner cell which in cross-section has 

 the form of a triangle, 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 division in all directions form the mass of sperm cells. 

 The first division wall 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 

 refringent, and in stained sections show a much more granular 

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

 cases studied, uses its nucleolus before the formation of the 

 spermatozoids begins. The latter in their structure and 

 d^elopment correspond with those of Sphagnum, but owing to 

 their smaller size are not favourable for studying the minute 

 details of development. 



In the peripheral cells are numerous chloroj^lasts which 

 lie close to the inner wall of the cell in the ripe antheridium. 



