LUTHER BURBANK 



experiments with tropical plants of the genus 

 Asclepias, relatives of the familiar milkweed. 



I have undertaken tentative experiments to dis- 

 cover whether these plants might be developed to 

 a stage that would make them commercially valu- 

 able as producers of rubber. The recent discov- 

 eries of the chemist make experiments in this line 

 somewhat less valuable than they hitherto seemed. 

 Yet the demand for rubber is so great, in these 

 days of electricity and automobiles, that there 

 seems little danger of overstocking the market. 

 And if a plant could be developed that could be 

 grown in temperate regions, and they would pro- 

 duce the rubber-forming juices in adequate quan- 

 tity, such a plant would constitute a very valuable 

 acquisition for a long time to come, even should 

 natural rubber ultimately be supplanted by the 

 laboratory product. 



The method of gathering the so-called latex, or 

 milky juice, which is virtually rubber in solution, 

 is curiously similar to the method of obtaining the 

 sap of the sugar maple. Indeed the latex may be 

 drawn in precisely the same way, by boring a hole 

 in the trunk of the rubber tree and inserting a 

 grooved stick along which the juice will run into 

 a receptacle. But the cultivators are not usually 

 content with so slow a method, and there are 

 various methods of tapping the tree that expose a 



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