THE GAMETOPHYTE 25 



are formed in some of these, so that the cover becomes to some extent double. 

 Jeffrey states that the cover is two layers throughout, but Bruchmann found that 

 some of the cells — two and sometimes three — remain undivided and that one of 

 these undivided cells functions as the opercular cell. I have examined this point 

 carefully in Botrychium virginianum and find that there is an opercular cell in this 

 species also. The division walls in the primary cover cell usually intersect at right 

 angles, so that the opercular cell is four-sided, instead of triangular, as in Ophio- 

 glossum (fig. 14, H); but exceptionally it may have the triangular form. In the 

 dehiscence of the antheridium only a single opercular cell is destroyed, not two 

 superimposed cells, as JeflFrey supposed to be the case. 



The divisions in the central cell are very much the same as in Ophioglossum. 

 Whether the first division is regularly transverse or vertical could not be determined, 

 as no examples of the first division were found. The earliest stages seen after the 

 first separation of the cover cell had four inner cells arranged quadrant-wise, but 

 it was not clear which was the primary wall. The quadrant division is, usually at 

 least, followed by an octant division, and these early divisions may sometimes be 

 recognized for a long while, as there is not much displacement of the cells due to the 

 subsequent divisions. In the later stages the primary divisions can no longer be 

 made out clearly. The number of sperm cells finally formed may be very large- 

 more than a thousand in the largest antheridia- thus nearly or quite equaling the 

 number found in Ophioglossum pendulum, although the sperm cells are very much 

 less in size than in the latter and the antheridium correspondingly smaller. Some- 

 times the antheridium is divided into irregular chambers, apparently due to the 

 persistence of some of the early division walls (fig. 15, B). 



Fig. 15. — Botrychium virginianum. 



A. Longitudinal section of a nearly ripe, but rather small, antheridium. X about 200. 



B. Section of a ripe antheridium which has discharged the spermatozoids; some cell-walls have remained, 



forming irregular chambers, and retaining some of the spermatozoids. 



C. A surface view of a ripe antheridium, showing square opercular cell. 



The antheridium of i?. lunaria, according to Bruchmann, is smaller than that 

 oi B. virginianum, but the size of the spermatocytes and spermatozoids seems to be 

 about the same (fig. 8, Z)). 



THE ANTHERIDIUM OF HELMINTHOSTACHYS. 



The antheridium of H elminthostachys has been studied by Lang, and it is 

 evident from his account that it resembles that of Botrychium much more than it 

 does that of Ophioglossum. As in the former, the primary cover cell undergoes 

 periclinal divisions as well as anticlinal ones, but there are from two to four cells 

 which do not divide by periclinal walls, and one of these cells becomes the opercular 

 cell (fig. II, C). These four undivided cells stain more strongly than the other cells 

 of the cover, but only one of them is broken down at the time of dehiscence. These 



