lli 



622 



A TEXTBOOK OF THEORETICAL BOTANY 



topographical ; they are also functionally distinct, and this renders any direct 

 comparison with the vascular bundles in Spermatophyta impossible. In the 

 latter group the bundles are common to both stem and leaf, that is, every 



Cortex 



Vallecular canal 

 * Endodermis 



Metaxylem 

 Protoxylem 

 Phloem 



Carinal canal 



Fig. 631. — Equisetum arreuse. Transverse section of 

 the rhizome. Note the highly sclerotic outer cortex. 



#*• <»■ 



y^ t^ 



"^ 



r/ 



.-»^ 





Carinal canal 



Fig. 632. — Equisetum arvense. A single vascular 

 strand. Much enlarged. 



