ORGANIC COMPOUNDS OF PLANTS 213 



germination, some of the carbohydrates are converted 

 into organic acids. 



The fatty acids are the characteristic constituents of 

 fats. In germinating seeds, fat is formed from starch by 

 the addition of oxygen. The pectose substances are 

 capable of being separated in the laboratory into glucose 

 and acid products. Likewise the glucosides may be split 

 up into glucose and acid bodies. In fact, the various non- 

 nitrogenous compounds of plants, considered as a whole, 

 are more or less related in chemical composition. 



290. Food Value of the Non-Nitrogenous Com= 

 pounds. As a class, the non-nitrogenous compounds 

 are valuable as heat- and energy-producing nutrients. 

 They do not all have the same caloric or fuel value ; for 

 example, a gram of starch yields 4.2 calories while a gram 

 of fat yields 9.2. As a rule, the more concentrated the 

 compound is in carbon, the greater is its fuel value. When 

 properly associated and combined with the nitrogenous 

 compounds, the non-nitrogenous nutrients of plants may 

 produce fat in the animal body. A few of the non- 

 nitrogenous compounds, as the essential oils, have but 

 little direct value as nutrients. Others, as some bitter 

 principles and tannic compounds, may lessen the value of 

 foods or impart a negative value. The carbohydrates, 

 fats, and related non-nitrogenous compounds take an im- 

 portant part in the nutrition of man and animals, and 

 many foods owe their value entirely to the fats and car- 

 bohydrates which they contain. 



