PTEEIDOPHYTA— EQUISETIN^ 



151 



A transverse section of the rhizome, taken a little way 

 from the growing point, shows its exterior divided mto ridges 

 and furrows. Opposite to each furrow there is, a little 



way from the surface. 

 Fig. 908. Fig. 909. a large lysigenous 



intercellular cavity. 

 These together are 

 known as vallecular 

 cavities. They] are 

 interrupted at the 

 nodes, where a sheet 

 of parenchymatous 

 tissue stretches across 

 them. 



Fig. 910. 



Fig. 908. Fertile stem of Equisettim beariug a 



flower or cluster of sporopbylls. Fig. 909. 



Sterile shoot of Equisetum. 



Fig. 910. Growing point of 

 shoot of Equisetum arvense. 

 X 250. a. Apical cell. 

 6, c. Successive segments 

 cut oS from it. 



A little mternal to 

 these cavities are the 

 several steles, the plant 

 being schizostelic. 



These are arranged 

 differently iu different 

 species, and we may 

 distinguish three va- 

 rieties. In E. Utorale 

 (fig. 911, a), the steles 

 are all separate, each 

 is clothed with peri- 



