The Plant. 97 



property assumes great importance, as a source of heat or energy, 

 when the fats are oxidized in the sprouting seed or in the animal 

 body. 



In some remarkable manner, the plant reverses this process and 

 constructs its fats from carbohydrates with elimination of oxy- 

 gen. The following figures show the relative composition of a 

 typical carbohydrate and a typical fat. 



Per cent Per cent Per cent 

 Carbon Hydrogen Oxygen 



Carbohydrate (starch) 39-98 6.71 53.31 



Fat (stearin) 76.78 12.45 10.77 



Fats occur in plants chiefly as reserves in the seed. The seeds 

 of cereal plants such as corn and oats contain only small amounts 

 of fat. Flaxseed, cotton-seed, the castor bean and other seeds 

 contain oil in sufficient amount to render its extraction on a com- 

 mercial scale both feasible and profitable. The fat content of 

 i'cme common seeds is as follows: 



Per cent 



Barley 1.8 



Whefct 20 



Con. 5.0 



Oats . 5.0 



Per cent 



Cotton 20.0 



Sunflower 21.0 



Flax 33.5 



Castor bean.. 50.0 



The old fashioned home process of soap-making by boiling 

 waste grease with leachings from wood ashes depends upon the 

 fact that alkali metals, in this case the potassium or ' * potash ' ' of 

 wood ashes, will displace glycerine from fats. Super-heated 

 steam also breaks up fats into glycerine and fatty acids, and in 

 common with the alkali treatment mentioned above, the process 

 is called saponification. The glycerine of commerce is a by- 

 product from this process in the soap industry. Since mineral 

 oils cannot be saponified, we have here a means of distinguishing 

 them from fats. 



Lecithin is a compound closely related to the fats. In place 

 of one part of fatty acid in a normal fat it contains phosphoric 

 acid combined with a nitrogen-containing, basic compound known 



