no 



MOSSES AND FERNS 



CHAP. 



the limits of the primary cells more difficult to follow. The 

 number of the cells, too, that contribute to the formation of 

 the capsule, cannot be determined exactly, and there is evi- 



FlG. 56. — Porella Bolaiulcri. A, Nearly median longitudinal section of an advanced 

 embryo, X260; B, the upper part of a similar embryo, X525; C, sporogenous cells 

 and elaters from a still older sporogonium, X52S. 



dently some variation in this respect, as there is in the time of 

 the separation of the capsule wall from the archesporium. 



