358 



MOSSES AND FERNS 



CHAP. 



a two-sided one. The further development of the cotyledon 

 corresponds almost exactly with Onoclea. It does not break 



Fig. 200. — A, Horizontal section of an advanced embryo of 0. Claytoniana, passing 

 through the cotyledon and foot, X230; B, longitudinal section of the stem apex 

 in a somewhat older embryo of O. cinnamomea, X460; C, transverse section of 

 the apex of the primary root of the same, X460. 



through the calyptra until later, and in this respect shows its 

 primitive character. The single vascular bundle of the petiole 



Fig. 201.— 'Transverse section of a prothallium of O. Claytoniana, showing the lateral 



position of the embryo {em), X75- 



approaches the collateral type, and is much like that of the 

 cotyledon of Marattia. Stomata of the usual type occur on 



