i4o THE STRUCTURE OF ECONOMIC PLANTS 



there is no production of additional ducts as a result of secondary 

 thickening. 



The pith consists of large thin-walled cells with intercellular 

 spaces, and prior to the disintegration of the centrally located ones, 

 they contain numerous crystals of calcium oxalate. Similar 

 crystals occur in the parenchymatous cells of the cortex, pericycle, 

 and phloem. 



-^ - ql hr 



I 



4 



I 



Fig. 115. Median longisection of apex of vegetative axis showing origin of latex ducts in 

 young leaves — diagrammatic : «x i, axillary bud ; ^/ z&r, glandular hair; i-r, hair; lad, 

 latex duct; /)/»/', protophloem ; p 1^ j, provascular strand ; /^ a:, protoxylem. 



