THE ANGIOSPERMAE : ROOTS 



809 



Primary xylem 



Cambium 



Fig. 803. — Cucurbit o pepo. Transverse section of a 

 tetrarch root showing secondary thickening. 

 Note the exceptionally large vessels which are 

 typical of climbing plants. 



n„'.. " '' yVi '\ Secondary phloem 





^OVJ^ii^ Seconder/ xy/em 





Primary xylem 





". xf, *-■■* ' -^ 



Fig. 804. — Cimidfuga racemoso. Transverse section of 

 part of a tetrarch root showing secondary thickening 

 with wide medullar>- rays. 



