140 TEXTBOOK OF BOTANY 



nent. When the water is decreased, condensation is prominent. A good 

 supply of sugars and a relatively low water content are two of the con- 

 ditions in plant cells that are conducive to fat synthesis. Fat accumulates 

 in seeds at a time when their water content is decreasing. 



Fat digestion in germinating seeds occurs when the water content of 

 the cells is increasing. It is easy to see how certain factors in the environ- 

 ment may affect these two internal conditions and thereby affect the 

 formation of fats. The highest percentage of linseed oil is obtained from 

 flax plants that grow in relatively dry climates with an abundance of 

 clear days. 



Fats not only are digested during the germination of seeds, but the 

 whole process of fat synthesis may be reversed, and the fat be recon- 

 verted to sugar. Both hydrolysis and oxidation-reduction occur in a com- 

 plete reversal of the process of fat synthesis. The transformation of fats 

 to simple sugars, of simple sugars to starch, of starch to simple sugars, 

 and of simple sugars to sucrose which moves down the stems to the 

 roots, may all be detected by microscopic studies of seedlings of soy- 

 beans. 



Of the 3 molecules of fatty acids that may unite with 1 molecule of 

 glycerin in fat svnthesis, all 3 may be alike, 2 may be alike, or all 3 may 

 be unlike. Since there are many kinds of fatty acids, many different 

 kinds of fats and oils are made bv plants and animals. 



This fact seems even more remarkable when we think of the trans- 

 formations that are characteristic of different species of plants and ani- 

 mals. A mouse eats corn. In its body some of the starch from the grain of 

 corn is digested to sugar which in turn is transfonned to fat, and some 

 of the corn oil is also digested and transformed to mouse fat. In the body 

 of the cat that eats the mouse, mouse fat is digested and transformed 

 to cat fat. These specific differences are of course due to different in- 

 herent systems of protoplasm and enzymes in the corn, mouse, and cat. 

 There are cases on record in which the cells of pigs failed to change all 

 the plant fat in their food (cottonseed meal) into pig fat, and some of 

 the cottonseed oil accumulated in the cells of the pigs. Similarly, turkeys 

 that were fed large quantities of cod-liver oil failed to convert all of it 

 into turkey fat. 



Although fats are present in every living cell as a part of the proto- 

 plasm, they are especially abundant in the cells of many kinds of seeds. 

 In addition to their use as food, fats are extracted from plants and used 

 in making soaps, paints, lubricants, and many other products. Some of 

 the commonest commercial fats and oils derived from plants are corn, 



