THE VASCULAR TISSrES. 



69 



(a) Ground-tissue rays are those portions of the fundamental 

 or ground-tissue in the stem or root of Dicotyledons and Conif erse 

 which exist between the primary vascular bundles before the 

 interfascicular cambium has arisen. When the secondary bundles 

 are formed by the activity of this cambium the cells of these 

 columns of tissue become, at first, compressed, and, finally, almost 



Fig. 5?. — A Longitudinal Radial Section of the Stem of Pinvs to 

 show the true medullary rays.— m, m, Medullary rays arising from 

 cells of the cambium {x, dotted in fig. ). 



obliterated. The component cells of the rays are similar in 

 structure to those of the cortex or ground-tissue, and the 

 centrally-situated mass of fundamental tissue, which is at first 



