436 



MOSSES AND FERNS 



CHAP. XIII 



conditions. The surface of the rhizome in E. telmateia, 

 especially at the nodes, is covered with a dense dark -brown 

 felt of matted hairs, and a whorl of roots occurs at each node, 

 corresponding in number to the number of axillary buds, from 

 whose bases the roots really grow. Sometimes the buds 

 become changed into tubers (Fig. 227), which are especially 

 common in E. telmateia and E. arvense. These tubes are 

 protected by a hard brown sclerenchymatous rind, within 

 which is a mass of starchy parenchyma, traversed by the slender 



Fig. 226. — A, An advanced embryo of E. arvense (L.), surface view, X360; B, optical section of a 

 similar stage of E. pahtstre (L.), x 360 ; C, older embryo of E. aniense (L.), X 160 ; st, stem ; R, 

 root (all the figures after Sadebeck). 



vascular bundles. In some cases these buds form in chains 

 and are then seen to be the swollen internodes of short 

 branches. 



The aerial stems are of two kinds, sporiferous and sterile. 

 In one group the only difference between the two is that the 

 former bear at the apex the sporangial strobilus ; in the second, 

 of which E. telmateia is an example, the sporiferous branches 

 are almost entirely destitute of chlorophyll and quite unbranched, 

 while the green sterile shoots are extensively branched. In 

 such forms the fertile shoots die as soon as the spores are shed, 

 and usually appear before the green shoots are developed. 



