THE GAMETOPHYTE 



23 



this projection is less marked, although this may be somewhat decided in the 

 ripe antheridium. The first division in the inner cell is usually vertical, but may be 

 transverse, at least in 0. pendulum (fig. 13, A). The second v^^alls intersect the 

 first at right angles, and there are always four nearly equal inner cells resulting 

 (fig- 13' -^)- The third set of walls is vertical, and the next, in some cases at least, 

 is in the same direction. This is not true, however, of the deeper and narrower type 

 of antheridium. Further divisions occur until the number of spermatocytes is very 

 large. The fully developed mass of spermatocytes is plainly visible to the naked 

 eye, and in 0. pendulum may reach a diameter of more than 325 At. 250 cells and 

 upward may be counted in a single section of a large antheridium, and this would 

 mean that there are several thousand in the whole antheridium — perhaps more than 

 in any other Pteridophyte. In 0. moluccanum (fig. 12), the number of spermatocytes 

 is much smaller, while in this regard the antheridium of 0. vulgatum appears to be 

 intermediate between that of 0. moluccanum and 0. pendulum. 



J^IG. iz. — Ophioglossum moluccanum. 



A. Ripe antheridium. Xi8o. 



B, C. Young antheridia. X320. 



D. Surface view of antheridium, showing opercular cell. 



The nuclei of the young cells show a conspicuous nucleolus, which becomes less 

 marked in the later stages of the antheridium. According to Mettenius, the outer 

 wall of the antheridium in O. pedunculosum is composed of two layers of cells; but 

 both Lang and Bruchmann found that the central part of this outer wall of the 



Fig. 13. — Development of the antheridium in Ophioglossum pendulum. 



A. Median section of gametophyte, apex, showing apical cell, x, and two young antheridia, 6 . X175. 



B. Transverse section of apex; *, apical cell. 



C. D. Median sections of young antheridia. 



E. Median section of a nearly ripe antheridium. 



F, Surface view of ripe antheridium; 0, opercular cell. 



