Stem and Root Structures 



77 



each bundle is surrounded by a fibrous sheath developed from 

 the ground tissue. 



Fig. 74. — Pdrt of a transverse section through the stem of Tradescantia 

 Sello'i : t», epidermis, with a sioma, sp ; R, cortex ; V, thickening ring with the 

 outer vascular bundles, ^ ; g'\ inner vascular bundles { x 75). 



Secondary Thickening in Monocotyledons. — Since 

 the closed bundles of monocotyledons allow for no secondary 

 thickening, the structure of the mature stem resembles that of 



