514 



MOSSES AND FERNS 



CHAP. 



at no time in ^. Kraussiana are they confined to this apical 

 region, as Miss Lyon states is the case in S. apus. 



With the increase in the amount of protoplasm, the very 

 large central vacuole becomes reduced in size, and finally, but 

 this does not occur until after the germination of the spore, is 



Fig. 296. — A, Young macrospore of Selaginella helvetica. The vesicular protoplast, 

 with the primary nucleus, is much smaller than the spore membranes, X400; B-E, 

 S. Kraussiana, sections of the older macrospore, showing the development of the 

 gametophyte; B, X about 200, the others more highly magnified; e, exospore; m, 

 mesospore; n, nuclei; D, E, show the first cell- formation; D, vertical; E, horizontal 

 section of spore-apex. (A, after Fitting). 



completely obliterated. In microtome sections it appears en- 

 tirely empty, but Heinsen ( i ) states that in the living state it 

 is occupied by great quantities of fatty oil. Whether this is 

 the case in S. Kraussiana was not investigated. 



