SOME USEFUL PLANTS AND PLANT PRODUCTS 321 



making soaps as well as in numerous other ways. Olive 

 oil, obtained by pressing the ripe fruit of the ohve tree, is the 

 most valuable for food purposes. It is largely adulterated 

 with other oils of vegetable origin, such as cottonseed oil, 

 obtained by grinding and pressing the kernels of cotton seeds, 

 and peanut oil, pressed from peanuts. Peanut butter is 

 made by grinding but not pressing the peanuts. The plant 

 from whose seeds castor oil is made belongs to the spurge 

 family. The oil is used in making soaps and lubricants, in 

 medicine, and in the 

 manufacture of oilcloth, 

 artificial leather, and cel- 

 luloid. Treated with 

 sulphuric acid, castor oil, 

 as well as olive oil or 

 cottonseed oil, forms 

 what is known as "tur- 

 key red oil," which is 

 largely used in treating 

 cotton fabrics so that 

 they can be colored with 

 certain coal tar dyes. 

 Linseed oil, made from 

 flax seed, has the prop- 

 erty of drying quickly if exposed to the air, leaving a 

 varnish-like residue ; this property makes it valuable in 

 paints and varnishes. Linseed oil enters into the manu- 

 facture of linoleum, and, when thickened by long boiling, 

 it forms the basis of printer's ink. Corn oil, made from 

 the embryos of corn kernels, is used as a substitute for 

 linseed oil in paints ; it is also used in making soaps 

 and lubricants. Corn oil, as well as linseed oil, can be 

 vulcanized by heating with sulphur, so forming a substitute 

 for rubber. An oil pressed from hemp seeds is also used, like 

 linseed oil, in paints and in soap-making. The kernel of the 



Fig. 178. — Peanut plants. 



