550 



MOSSES AND FERNS 



CHAP. 



entiated elements, the rest of the bundle showing only elongated 

 parenchyma, much like the original procambium cells. 



The axis of growth of the primary root usually coincides 

 with that of the cotyledon, but this is not always the case. In 



Fig. 318.— a, Median section of a young sporophyte with the second leaf U already 

 formed; r^, second root; st, stem-apex, X150; B, cross-section near the base of the 

 cotyledon, showing the intercellular spaces i and the second leaf U surrounded by 

 the sheath v at the base of the cotyledon; /, the ligule of the cotyledon, X300. 



the very young root (Fig. 317, R) the end is covered with a 

 layer of cells continuous with the epidermis of the rest of the 

 embryo. Beneath are two layers of cells concentric with the 



