Stem and Root Stnictuir^s 



77 



each bundle is surrounded by a fibrous sheath developed from 

 the ground tissue. 



Fig. 74. — P.irt of a transverse section through the stem of Tradescaniia 

 St'//i>i' : ('. epidermis, \\ith a sioma, s/ ; R, cortex ; V, thickening ring with the 

 outer vascular bundles, g' ; j;^", mner 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 



