IX 



FILICINE^ LEPTOSPORANGIAT^ 



315 



it arises from a protrusion of the cell which is cut off by a wall, 

 w^iich is usually somewhat oblicjue. The papilla thus formed 

 enlarges and soon becomes almost hemispherical. It contains 

 a good deal of chlorophyll and a large central nucleus sur- 

 rounded by dense cytoplasm. The first wall in the young an- 

 theridium (Fig. 174, A) is very peculiar. It has usually the 

 form of a funnel, whose upper rim is in contact with the wall of 



Fig. 174. — Onoclea struthiopteris. Development of the antheridium. A-C, Vertical 

 section, X6oo; D, two nearly ripe sperm cells; E, free spermtatozoid, X about 



1200. 



the antheridium cell, and whose base strikes the basal wall of 

 the antheridium. Sometimes this first wall does not reach to the 

 base, in which case it is simply more or less strongly concave, 

 and the basal cell cut off by it from the antheridium is discoid 

 instead of ring-shaped (Fig. 174, B). The second wall is 

 hemispherical, and is nearly concentric with the outer wall of 

 the antheridium. The dome-shaped central cell produces the 



