202 



BOTANY AND PHARMACOGNOSY. 



While the cambium is developing xylem and phloem, another 

 meristem, known as the phellogen^ arises beneath the endo- 

 dermis. It produces upon the inside parenchyma, known as the 



E 



SM 



Fig. 112. Fully developed secondary structure in root. Transverse section of root 

 of pea (Pisum) at the end of the summer's growth: E. some epidermal cells ^^-ith fragments 

 of root hairs; C, primary cortex; EN, endodermis; K, cork; B, bast fibers; SC, secondary 

 cortex; S^ sieve; T, ducts; W, wood fibers; WP, wood parenchyma; PM. primary medul- 

 lary rays; SM, secondary medullary rays; the xylem and phloem forming open collateral 

 iibrovascular bundles , these being found in dicotyledons with but few exceptions. 



SECONDARY CORTEX (SC), and upon the outside, cork (K). This 

 stage in the growth of the root marks the completion of the devel- 



