294 



PLANT STRUCTURES 



FIG. 276. Cross-section of the vascular axis of a root, showing radiate type of bundle 

 the xylem (p) and phloem (ph) alternating. After SACHS. 



found in stems. The xylem is in the center and sends out 

 a few radiating arms, between which are strands of phloem, 



forming the so-called 

 radiate bundle (Fig. 276). 

 This arrangement brings 

 the tracheary vessels 

 (xylem) to the surface of 

 the bundle region, which 

 is not true of either the 

 concentric or collateral 

 bundle. This seems to 

 be associated with the 

 fact that the xylem is to 

 receive and conduct the 



FIG. 277. Endogenous origin of root branch- water absorbed from the 

 es, showing them () arising from the cen- -i T- i ^ i ., 



tral axis (/) and breaking through the 



cortex (r).-After VINES. that this characteristic 



