134 LUTHER BURBANK 



tured so cheaply as to compete successfully with 

 the natural product of the indigo and madder 

 plants. What was a large plant industry only a 

 few years ago has thus ceased to have impor- 

 tance. The indigo plant is still cultivated in the 

 east, but the entire industry has been changed by 

 the discoveries of the chemist. 



Only a few years ago a plant known as the 

 tarweed (Madia), to which we have had occa- 

 sion to refer in another connection, was gathered 

 and its juices extracted for the making of mad- 

 der. 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 sub- 

 stituted for a plant industry an enterprise asso- 

 ciated with the manufacture of gas. 



It will doubtless be a long time before the man- 

 ufacture of artificial rubber makes correspond- 

 ing 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 great 

 and important one, and the principal trees that 

 supply the juices that on evaporating constitute 

 rubber are cultivated in vast plantations in vari- 

 ous tropical regions. Moreover rubber is gath- 



