394 PLANTS AND MAN 



a finish which is tough, elastic, and much less liable to crack 

 than those obtained when the copals and other hard resins are 

 used. The oil cake left after pressing out the oils is poisonous, 

 and unfit for use as stock food. 



Numerous other drying oils are used in paints and varnishes, 

 linoleums, oilcloths, soaps, preservatives for leather and canvas, 

 and sometimes as illuminants. A few of these are candlenut oil 

 and WALNUT oil from tree sources, and poppy oil, perilla oil, 

 and SUNFLOWER OIL from herbaceous plants, all* derived from 

 seeds. 



***** 



Cottonseed oil, of which the United States is chief producer, 

 is the most important of the semi-drying oils, as well as being the 

 most abundantly produced plant oil. This has developed as a by 

 product of the cotton industry, by which cotton seeds were re- 

 garded merely as waste prior to 1880. Today over one hundred 

 million gallons of oil are produced annually, and the residue, or 

 cake remaining after expressing the oil, is an important stock food 

 and fertilizer. Cottonseed oil is most widely used as a salad and 

 table oil and in the manufacture of butter and lard substitutes. 



Soybean oil is of increasing importance in American agri- 

 culture. It is produced from the seed of the soybean, a native of 

 eastern Asia, and long an important agricultural plant in that 

 region. In the United States, soybean production centers in 

 Illinois, which produces about one-half of the total soybeans 

 grown here. In its drying characteristics, soybean oil stands mid- 

 way between linseed and cottonseed oils, hence is useful in the 

 manufacture of varnishes, printing inks and soaps, in addition to 

 being of importance as a salad oil and for other edible purposes. 

 Considerable use is being made of soybean oil and soybean flour 

 as raw materials in the manufacture of certain types of molded 

 plastics used in automobile manufacture. 



Corn oil, like cottonseed oil, was formerly a waste product, 

 but today the embryos from corn grains are pressed for their oil 

 which is used after refining for cooking and baking. Crude corn 

 oil is used industrially in the manufacture of cheap paints, soaps, 

 and rubber substitutes. 



