448 



MOSSES AND FERNS 



CHAP. 



buds remain otherwise undeveloped. In the aerial stems the 

 roots remain normally undeveloped, but may often be stimulated 

 into growth by keeping the stem moist and dark. 



Van Tieghem ^ describes the roots of E. palustre as being 

 exogenous, and says they can be traced to a definite cell of one 

 of the young segments. Janczewski,^ however, was unable to 

 recognise the young root until the first foliar sheath was well 

 developed, and in E. telmateia I could see no trace of the 

 root in still older buds, and they were apparently always of 



Fig. 235. — A, Longitudinal section of the root apex, X200; jr, x, the large central vessels of the 

 vascular bundle ; B, C, two transverse sections passing through the apex, X 200. In C is shown 

 the: first divisions of the cap cell. 



endogenous origin, although this point was not closely in- 

 vestigated. 



The structure of the apical meristem is much 

 the leptosporangiate Ferns, the main difference being 

 development of the root-cap, in which periclinal 

 frequent, so that the older layers, especially in the 

 several cells thick, and not clearly limited. 



After the sextant walls are formed, each semi 

 divided at once into an inner and an outer cell, the former 



like that of 



the greater 



walls are 



middle, are 



segment is 



1 Van Tieghem (5), p. 551. 



- Janczew.ski (3), p. 89. 



