142 LUTHER BURBANK 



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 testing tropical plants as to pro- 

 duction of useful commercial products, and for 

 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 compounds 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 con- 

 stituents as protoplasm itself and differ from the 

 gum and resins that we have just been consider- 

 ing in that each molecule contains at least one 

 atom of nitrogen. 



The sugars, it will be recalled, occupy an in- 

 termediate place, inasmuch as they, unlike the 

 resins and rubber, contain oxygen ; but they con- 

 tain no nitrogen. The formulae given by the 

 chemist for the different alkaloids are intricate 

 but they differ from one another only in the mat- 

 ter of a few more or a few less atoms of one or 

 another of the four constituents of which they are 

 all made up. 



