CHAPTER III 



PLANT COMPOUNDS 



In the preceding chapters several plant compounds have 

 been discussed with reference to their uses in the plant, 

 their method of formation, and some of the natural changes 

 that take place in them. Besides these few compounds 

 already mentioned there are a very large number produced 

 during the growth of plants. Some plants form one kind, 

 some another. Many of the compounds have no value com- 

 mercially, and no known value physiologically. Some are 

 evidently merely by-products, whereas others undoubtedly 

 serve some useful purpose to the plant. Since many of these 

 compounds are of great importance to the human race, it 

 is necessary to know something of their properties and uses 

 outside of the plant. In the following discussion only those 

 plant compounds which are of known physiological impor- 

 tance to the plant, and particularly those which are of 

 economic importance to mankind, will be considered. For 

 convenience the various compounds will be grouped as 

 follows : 



I. Carbohydrates 

 II. Fixed Oils and Waxes 



III. Volatile Oils and Resins 



IV. Nitrogenous Compounds 



V. Organic Acids and their Salts 



I. CARBOHYDRATES 



50. General Definition. — The most abundant group of 

 organic compounds is that of the carbohydrates or sac- 

 charides, comprising about 75 per cent, of the dry matter 

 of plants. Popularly, a carbohydrate is defined as a com- 

 pound containing carbon, hydrogen, and oxygen, with the 



