70 



THE PLANT CELL, 



connected to the cortex by means of the rays, becomes, later on, 

 the pith or medulla, 



(h) True or secondary medullary rays are, on the other hand, 

 formed from special cells of the cambium, and stretch out from 

 this both ways into the xylem and phloem. At times a ray may 

 pass right through both, so as to connect pith and cortex ; but, 

 as a rule, the rays end in the xylem and phloem (see Fiq. 5l'). 



Fig. 5.3. ^Portion of a Transverse Ski- 

 Tioy OF THE Stem ok Pinus to show 

 the course of a medullary ray through 

 the xylem and phloem and into the 

 cortex. — X, Cambium ; xi/, xylem ; 

 phj, phloem ; ph.^, bast-fibres. 





Fig. ."4 —Medlllarv Ray 



SEE.V IN A TaNOKNTIAL 



Longitudinal Skctio.s 

 OK A Stem of Pinus.— 

 t, Tracheidea ; m/l, me- 

 dullary ray cells. 



