PLANT ORGANS AND ORGANISMS 
129 
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 }>£ 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 
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