THE CANNA AND CALLA 43 



tutes for the natural ones, has given clues that the 

 plant developer is beginning to take up. 



I have been requested, for example, to im- 

 prove the clove and the cinnamon, as well as the 

 coffee plant, in the production of races having a 

 higher percentage of the various essential oils for 

 which they are prized. 



Coffee, as everyone knows, depends very 

 largely on its aroma and fragrance, and it has 

 been found that these may be greatly modified 

 according to the soil in which the plant is grown. 

 The fragrant qualities are often greatly intensi- 

 fied when the plant is grown on volcanic soil and 

 at a high altitude. It is known that various 

 spices differ markedly. In the same way the 

 quality of alkaloids, such as caffeine and quinine, 

 may vary in the same species under different 

 conditions of soil and climate. There is a species 

 of coffee that is practically without caffeine ; but 

 this has little aroma. It has been proposed to 

 combine it with the Arabian coffee and it may be 

 possible to produce a coffee without caffeine — 

 which may or may not be popular. 



Among garden plants that are prized for their 

 aromatic quality, the thymes vary widely in the 

 amount and quality of their essential oils. 



The notable variation in the odor of the calla, 

 which gave the scented variety, is duplicated in 



