242 



MOSSES AND FERNS 



CHAP. 



endophytic fungus. The upper portion, hghter in colour, bears 

 the reproductive organs. Some of the prothalha bear only 

 antheridia; the others have archegonia as well. As usual, the 

 first antheridia appear before any archegonia are formed. Both 

 archegonia and antheridia resemble those of Botrychium more 

 than they do those of Ophioglossiim. 



The Embryo 



The fertilised tgg, or oospore, becomes invested with a cell- 

 membrane and enlarges to several times its original bulk before 



Fig. 130. — Botrychium Virginianum. A, two-celled embryo within the archegonium 

 venter, X about 300; B, two sections of an 8-celled embryo; C, large embryo 

 showing the primary organs, X about 25. 



the first division wall is formed. This primary (basal) wall is 

 in most cases transverse, but may be somewhat oblique. The 

 two cells are generally more or less unequal in size, the upper or 

 epibasal cell being larger than the lower (hypobasal) one. 

 Each primary cell is next divided by a median vertical wall, and 

 the young embryo shows thus a regular quadrant formation. 

 The next divisions occur in the epibasal quadrants and are also 

 approximately transverse ; at this stage, to judge from Jeffrey's 

 figures 43, 44, the embryo presents a striking resemblance to a 

 corresponding stage in Anthoceros. 



