ON GUM AND SUGAR TREES 



refer in another connection, was gathered and its 

 juices extracted for the making of the pigment 

 madder. But it would not pay to undertake this 

 work now, since the chemist has learned how to 

 make madder from coal tar and hence has substi- 

 tuted for a plant industry an enterprise associated 

 with the manufacture of gas. 



It will doubtless be a long time before the 

 manufacture of artificial rubber makes corre- 

 sponding encroachments on the industry of manu- 

 facturing rubber from the plant juices. Still it is 

 quite within the possibilities that this may come 

 to pass in the course of the coming generation. 



In the meantime, the rubber industry is a vastly 

 important one, and the principal trees that supply 

 the juices that on evaporating constitute rubber 

 are cultivated in vast plantations in various trop- 

 ical regions. Moreover rubber is gathered from 

 wild trees of several species, although in recent 

 years the cultivated trees have largely been de- 

 pended upon to meet the growing needs of the 

 industry. 



Trees of the genus Hevea are the most import- 

 ant source of rubber. But there are many other 

 trees, the juices of which contain the essential con- 

 stituents of rubber in the right combination, and a 

 good many of these have commercial possibilities. 



I have referred in another connection to my 



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