THE GAMETOPHYTh 



129 



angles to the primary division wall. The next divisions are, usually at least, anti- 

 clinals (fig. 97, G), but before long the periclinal walls also are developed and sub- 

 sequent divisions do not show any recognizable regularity in their sequence; there 

 seems to be a good deal of variation in this respect, even in the same species. The 

 number of cells ultimately formed varies a good deal, but the number of spermato- 

 cytes finally developed is probably never so great as that found in some of the 

 Ophioglossaceae. Kaulfiissia, both in the size of the antheridium and that of the 

 spermatozoids, approaches nearest to Ophwglossum. The number of spermatozoids 

 may reach several hundred, fifty or more being visible in a single section of a large 

 antheridium, and nearly or quite as many may sometimes be found in Dantsa, 

 where, however, the spermatozoids are much smaller than in Kaulfussia. 



In the cover cell the divisions are all anticlinal and horizontal sections or 

 surface views show that the successive walls are arranged spirally in away suggesting 

 the segmentation of a three-sided apical cell. The last-formed wall cuts out a small, 

 nearly triangular cell, the opercular cell (fig. 95 D, E, 0). In most cases, at least, 



Fig. 98. 



Ripe antheridium of D. jamaicensis. m, mantle cells, 

 o, opercular cell. X350. 



Fig . 



99. 



A. Transverse section of three young antheridia of D. jamaicensis. 



B. Surface view of the two youngest ones. 0, opercular cell. X380. 



this opercular cell is thrown off when the antheridium opens, leaving a small 

 aperture through which the spermatozoids are ejected. Surrounding the mass of 

 spermatocytes is a layer of mantle cells cutoff from the adjacent cells of the prothal- 

 lium. These mantle cells, at the time of the opening of the antheridium, become 

 very much distended and project strongly into the cavity of the empty antheridium 

 (fig. 100, B, m). They no doubt play an important part in the dehiscence of the ripe 

 antheridium. 



SPERMATOGENESIS. (Plate 2, figs 38-44.) 



Of the Marattiaceae, Kaulfussia is the most satisfactory for studying the details 

 of spermatogenesis, owing to the much larger size of the spermatozoid. The 

 development of the spermatozoids agrees very closely in its details with that of 

 Ophioglossum. If the spermatocyte is examined just before the final division the 

 two blepharoplasts can be seen and the division of the cell into the two spermatocytes 

 proceeds very much as in Ophioglossum. After the final division the nucleus of the 

 spermatocyte appears coarsely granular and, as in other cases, no nucleolus can be 

 seen. In favorable cases the blepharoplast is visible as a round body, stained 



9 



