264 



MOSSES AND FERNS 



CHAP. 



root, and a very much shorter one to the young stem apex, 

 which Hes close to the base of the cotyledon. The outer layer 

 of cells of the cotyledon forms a pretty clearly defined epidermis 

 separated from the axial procambium strand by several layers 

 of young ground-tissue cells. 



The apex of the young stem is occupied in some cases, at 



Fig. 137. — Marattza Doug^lasii (^'Bzk.er). A, B, C, Three transverse sections of a root from the young 

 sporophyte; A shows the apical cell {x), X215 ; D, longitudinal section of a similar root, X260 ; 

 E, vascular bundle of the root, X 260. 



least, by a single apical cell, which probably is to be traced back 

 directly to one of the original octants of the embryo. Whether 

 this is always the case in the youngest stages cannot be de- 

 termined until further investigations are made. Farmer ^ was 



^ Farmer (3), p 267. 



