PTERIDOPHYTA 



289 



D. 



PIG. 254. Marsilia vestita. Germination of the macrospore. A, longitudinal section 

 of ripe macrospore (X 60) ; n, nucleus. B-G, successive stages in the development 

 of the archegonium (x360). C, E, transverse sections, c, neck canal-cell; 

 6, ventral canal-cell. 



PIG. 255. Pilularia ylobulifera. A, section of young sporophyte still enclosed in 

 the calyptra, cal. ; ar, neck of archegonium ; cot, cotyledon ; st, stem-apex ; 

 gp, macrospore (X 75). B, root, r, and stem-apex, st, of the same (X 215). 

 u 



