X 



FILICINEA£ LEPTOSPORANGIATJZ 



this divides the plerome from the cortex. After this in the 

 outer of the primary cells there is a separation of an outer from 

 an inner cell, the former giving rise either directly or by a 

 subsequent division to a single layer of cells upon the outside 

 of the root, which is usually regarded as the epidermis, and the 

 inner cells form the cortex. The inner layer of the cortex, 

 which can be traced back almost to the summit, is the 

 endodermis, and its radial walls are peculiarly folded. 



P'iG. 165. — Adiatituin ciiiarginntiim (Bory). A, Longitudinal ; B-E, a series of transverse sections 

 of the root, x 200 ; .r, apical cell : s-s, sextant walls ; en, endodermis. 



According to Strasburger,^ in Pteris Cretica the cap cells 

 divide only by perpendicular walls, and the older layers of the 

 cap remain but one cell in thickness. Van Tieghem -^ states, 

 and I have verified this in Adiantiivi eniarginattnn and 

 Polypodiuni falcatinu, that with the exception of the first- 

 formed cap cell (or " epidermal segment," to use his termino- 

 logy), there is, in the central part, always a doubling of the cells 



^ Strashurger (10). 



- Van Tieghem (5), p. 532. 



