XII 



LEPTOSPORANGIA TrE HETEROSPOREA^ 



381 



In AzoUa the contents of the ungerminated microspore, 

 whose wall is thin and smooth, contain but little granular 

 matter. The first indication of germination is the rupturing of 

 the exospore along the three radiating ventral ridges, and the 

 protrusion of a small papilla. This is cut off by a transverse 

 wall near the top of the spore cavity, and forms at once the 

 mother cell of the single antheridium (Fig. 197, C). Belajeff^ 

 says the next divisions are nearly parallel and divide the 

 antheridium into three cells, one above the other, and of these 



YiQ. \t)-].—AzoUa Jilictdoides (Lam.)- A, Massula with enclosed microspores {sp\ X250; gl, 

 glochidia; B-D, development of male prothallium and antheridium, X560; 0, opercular cell; E, 

 two cross-sections of a ripe antheridium, X 750 ; i, the top ; 2, nearly median section. 



only the middle ones divide further. For some reason, which 

 is not quite clear from his account, Belajeff does not regard the 

 whole upper cell as an antheridium, but says that the latter is 

 only formed after five vegetative cells have been cut off. It 

 seems much more in accordance with the structure found in the 

 related homosporous Ferns to regard the whole upper part of 

 the prothallium as the antheridium. In spite of his statement 

 that the development of the male prothallium has little in 



1 Belajeff (3), p. 329. 



