LUTHER BURBANK 



seed oil, with some flavoring added, serves the 

 purpose of the original spruce gum so the latter is 

 now seldom seen in the market. More recently 

 chicle, a gummy substance which exudes from 

 several tropical trees, has been imported in great 

 quantities, and is now supplanting all other sources 

 of gum. 



The supplying of turpentine and its products 

 gives the conifers high range among trees that 

 produce commercial by-products of great import- 

 ance. But with the exception of the pines, the 

 trees that produce really important exudates or 

 oils or chemicals are indigenous to the tropics, or 

 at least are confined to the warm temperate zone. 

 I have thought many times in recent years that I 

 should like to have a plant laboratory in the 

 tropics for the testing of tropical plants as to the 

 production of useful commercial products, and for 

 the development of improved varieties of plants 

 the products of which are already utilized. 



It would be worth while, for example, to make 

 very extensive experiments by way of testing the 

 qualities of the different trees that deposit in their 

 bark the bitter compound known as alkaloids, a 

 galaxy of which are prized for their medicinal 

 properties. These are very complex combinations 

 of carbon, hydrogen, oxygen and nitrogen. That 

 is to say, they have the same constituents as proto- 



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