THE ANGIOSPERMAE : STEMS 



88] 



Cortex 



Endodermis 



Pericyde 



I ^ J 



Fig. 867. — Agropyron repens. Transverse section of 

 rhizome showing the strongly thickened endodermis. 



Fig. 868. — Clintonia sp. Transverse section of stem 

 showing a ring of concentric vascular bundles each 

 with its own endodermis. 



The stele is not the only organ of the stem to possess a sheath, since many 

 glandular passages are similarly protected, nor does the stelar sheath always 

 have a true endodermal character. In a great many stems the layer sur- 

 rounding the stele is marked by the presence of large starch grains, although 

 29 



