RUBBER AND GUTTA-PERCHA 157 



products, which are not uncommonly present in considerable 

 quantity in the latex, probably render these plants distasteful 

 to animals. 



Those plants, whose latex contains a considerable percentage 

 of caoutchouc-particles, are of great economic importance, since 

 they are the source of the rubber and gutta-percha of commerce. 

 Para-rubber is obtained from a member of the Spurge-family 

 (Hevea brasiliensis) in which, however, the latex is contained in 

 laticiferous vessels. Other kinds are Ceara-rubber (from Manihot 

 glaziovii, a member of Euphorbiacese) , African rubber (from 

 species of Landolphia, which belong to the family Apocynaceae) , 

 and those obtained from the Indiarubber plant (Ficus elastica) 

 and from Castilloa elastica (Central America). Gutta-percha is 

 derived from diverse members of a tropical family, the Sapotaceae, 

 but here the latex is contained in vertical rows of cells. 



The latex is obtained by making V-shaped or herring-bone 

 cuts in the bark of the tree and collecting the exuding juice in 

 a small cup. The flow is maintained by paring off thin slices 

 from the lower edges of the sloping cuts, so that the latex- tubes 

 are kept open. After the latex has been artificially coagulated 

 it is washed, and thereupon the raw product is vulcanised. The 

 process of vulcanisation or curing involves a combination with 

 sulphur in varying proportions, according to whether soft rubber 

 or vulcanite is required. 



