350 



MOSSES AND FERNS 



CHAP. 



the embryo. Otherwise it nearly coincides with this. The 

 original three-sided apical cell persists for a long time, and it 



Fig. 178. — A, Horizontal section of an advanced embrj'o of O. Claytoniana, passing through the 

 cotyledon and foot, X 230 ; B, longitudinal section of the stem apex in a somewhat older embryo 

 of O. cinnamoiiica, X 460 ; C, transverse section of the apex of the primarj' root of the same, 

 X460. 



could not be positively shown whether or not it was afterwards 

 replaced by a two-sided one. The further development of the 



Fig. 179. — Transverse section of a prothallium of O. Claytoniana, showing the lateral position of the 



embrj'o (e7n\ x 75. 



cotyledon corresponds almost exactly with Onoclea. It does 

 not break through the calyptra until later, and in this respect 



