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Elementary Biology. 



or green cortex. The cork cambium itself is often known as 

 phellogen. These successive layers of cork form the bark ; 

 even in young twigs little patches of cork form below the 

 epidermis (usually beneath a stoma) and bulge it outwards, 

 forming what are known as lenticels. 



In the cortex, and frequently amongst the other tissues 

 as well, are found vessels of an entirely different character 



FIG. 9^. ORIGIN OF CORK. (Sachs.) 



f, epidermis ; A', cork or periderm ; /*/*, phellogen, or cork cambium ; 

 pd, phellodenn. 



from those already described. Two forms will be here de- 

 scribed, the laticiferous vessels and the resin canals. 

 Laticiferous vessels usually run in an irregular manner 

 through the tissue in which they are found. They branch 

 and anastomose. They contain a watery fluid known as 

 latex, seen very well exuding from the cut stem of a dande- 

 lion. The latex is not always white, however. It may be 

 red, blue, or yellow. Some varieties of latex are of great 

 commercial value, such as, for instance, india-rubber, gutta- 



