xin EQUISETINE.E 443 



E. arvense, and several other species, there is a common endo- 

 dermis {¥\g. 231, ai). In others the arrangement is different.' 

 Thus in E. liiiiosicm, each separate bundle has its own endo- 

 dermis ; in E. hievinle there is a common inner as well as an 

 outer endodermis in the aerial stems, while the bundles of the 

 rhizome are like those of E. limosuvi. Inside the endodermis lies 

 the single pericycle. 



All the cortical cells are separated by small intercellular 

 spaces, which are very conspicuous in the soft tissue of the 

 fertile stems of E. tclniatcia and E. arvense. In all of the 



Fig. 231. — Transverse section of the vascular bundle of a fully-developed vegetative shoot, X75 

 lacunae ; x, .r, tannin cells ; t, i, remains of the primary tracheids ; en, endodermis. 



internodes of the main axes of E. tehnateia chlorophyll is 

 absent, but in most species the principal assimilative tissue is 

 situated here. It consists usually of isolated masses of trans- 

 versely extended green cells separated by strands of colourless 

 sclerenchymatous fibres, which form the ridges so prominent 

 upon the internodes and foliar sheaths. Seen in cross-section 

 the masses of green cells are concave outwardly and lie 

 beneath the grooves between the ridges. In secondary branches 



1 Pfitzer (l), p. 292 ; Van Tieghem (6), p. 365. 



