PLANT ORGANS AND ORGANISMS 



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phloem tracts. Each of these constitutes a mass of protophloem 

 (first formed phloem). On the inner face of each phloem mass may 

 be seen intrafascicular cambium. At the outer end of each xylem 

 tract there has been Cut off a patch of fine cambial cells (interfascic- 

 ular cambium) which becomes joined to the intrafascicular cambium 



FIG. 62. Photomicrograph of a transverse section of a California Privet root 

 made about 1)2 inches above the root tip and showing transition structure. The 

 epidermis (e), primary cortex (pc) and endodermis are in the process of stuffing 

 off, since cork (ck) has been laid down by the cork cambium (ph) directly beneath 

 the endodermis. The cork cambium has also formed several layers of secondary 

 cortex (sc) on its inner face. The protophloem represented largely by hard 

 bast (hb) has been pushed out, while a small amount of secondary phloem repre- 

 sented by soft bast (sb) has been deposited beneath it by the cambium (c) which 

 now is nearly circular in aspect. The protoxylem (px) has been pushed into the 

 center by the encroaching secondary xylem (x) which has been laid down by 

 the cambium on its inner face. Highly magnified. 



to develop secondary phloem on the outer face and secondary xylem 

 on the inner face. 



C. Mount permanently a third T. S. out through the same root a 

 short distance above the second. Note that this is still larger in 

 diameter than the second. The pericambium has already divided 



