264 TROPICAL AGRICULTURE 



oils which are used in perfumes or for scenting toilet articles 

 are obtained, as already indicated in discussing perfumes, by 

 the process of enfleurage. This process consists merely in 

 saturating the material with warm fat and dissolving out the 

 essential oil by means of alcohol. The United States imports 

 essential oils to the value of more than $4,000,000 per year. 

 In the following discussion the oils are grouped together ac- 

 cording to their physical properties under drying oils, semi- 

 drying oils, nondrying oils, vegetable fats, and essential oils. 



DRYING OILS 



Perhaps the most important and most widely used drying 

 oil is Chinawood oil, which is obtained from the nuts of a 

 number of species of Aleurites. This genus includes at least 

 six species of trees, all of which produce oil-bearing nuts. The 

 oil obtained from these trees has long been favorably known 

 for use in various trades and is destined to become of still 

 greater importance. The cultivation of Chinawood oil trees 

 is extremely simple. They require only a moderate amount of 

 rainfall and appear to thrive in almost any soil. In fact, it 

 has been generally observed that these trees may be success- 

 fully grown on land which is too rough or otherwise unsuited 

 for ordinary agriculture. The trees begin bearing from seed 

 within 3 to 5 years. 



In China, there are two distinct species of economic im- 

 portance. The wood oil tree (A. montana) grows chiefly in 

 the subtropical parts of southeastern China. It appears to 

 require a warmer climate and more rainfall than the tung oil 

 tree (A. fordii). The wood oil tree in size and habit of growth 

 and general appearance resembles the tung oil tree. The 

 flowers are smaller and less conspicuous. The amount of oil 

 exported from this tree is much less than the export of tung 

 oil. The tung oil tree is much more widely distributed than 

 the wood oil tree and furnishes at least nine-tenths of the 



