486 



MOSSES AND FERNS 



CHAP. 



account of the female prothallium given here is based upon the 

 writer's observations upon wS. Kraussiana, made from microtome 

 sections of spores treated with chromic acid and embedded in 

 paraffin. 



The Microspores and Male Protkalliuni 



The microspores of all species of Selaginella are small 

 and of the tetrahedral type. According to Belajeff^ they may 

 show either a distinct perinium, or the latter is not clearly 



Fig. 253.— a, B, C, Three views of the young antheridium of Selaginella Kraussiana (A. Br.), X 450 ; 

 D, an older stage of the same, X480 ; E, F, two views of an older antheridium of 6". stolonifera, 

 X480; G, spermatozoids of 5". cuspidata (Sk.), X1170 ; x, vegetative prothal'.ial cell ; s, central 

 cells (after Belajeff). 



separated from the exospore. The spores contain no chloro- 

 phyll, but much oil as well as solid granular contents. At 

 the time that the spores are shed each one has already 

 divided into two very unequal cells, a very small lenticular cell 

 (Fig. 253, x) and a much larger one which, as in Isoetes, 

 becomes the single antheridium. 



The first wall in the antheridium divides it into two equal 

 cells, each of which then divides into two others, a basal and 



1 Belajeff (I). 



