528 



BOTANY 



PAET II 



The microspores begin their development while still enclosed within the 



A 



FIG. 494.^!, Selaginella helvetica (from 

 nature, nat. size). B, Selaginella Kraus- 

 siana, embryonic plant with macro- 

 spore still attached. (After BISCHOFF, 

 magnified.) 



FIG. 495. Selaginella helvetica. A, Macrospor- 

 angium from above showing the line of dehis- 

 cence (cl). B, Opened, seen from the side ; the 

 four macrospores, C, have been ejected. D, 

 Microsporangium in the axil of its sporophyll. 

 E, The same, opened. F, Microspores. (x 

 about 15.) 



FIG. 496. A -E, Selaginella stolonifera, successive stages in the germination of a microspore ; 

 p, prothallial cell; w, wall-cells of antheridium ; s, spermatogenous cells; A, B, D, lateral, 

 C, dorsal view. In E the prothallial cell is not visible, the disorganised wall-cells enclose 

 the spermatozoid mother cells ; F, sperm atozoids of Selaginella cuspidata. (A-E x 640, 

 F x 780. , After BELAJEFF.) 



sporangium. The spore first divides into a small lenticular vegetative cell, which 



