PLANT PRODUCTS 130 



functions in most cases are not definitely known. Chlorophyll 

 appears to be. the most important and is usually formed in 

 the chloroplasts. 



The function of chlorophyll in the formation of carbohy- 

 drates, the very first step in the making of true foods, has been 

 referred to (page 17) and will receive further consideration 

 in Chapter XVI. , 



Carotin and xanthophyll are always associated with chloro- 

 phyll. The various colors of flowers, fruits, leaves and other 

 parts of the plant are dependent on these pigments. 



Calcium oxalate is found in many plants and is readily seen 

 in various crystal forms. Many other compounds crystallize in 

 plants and may be very generally recognized by their forms. 



Many acids are found in plants, especially in the fruits, or 

 are derived from plant products by fermentation. Among the 

 most important are malic acid, oxalic acid, citric add, tartaric 

 acid, tannic acid and many others, especially the fruit acids, 

 which in a great measure determine the flavor and quality of 

 our edible fruits. 



Proteins are essential to the formation of living protoplasm 

 and, therefore, may be considered the most important of the 

 plant products. They are probably formed in the leaves in a 

 manner somewhat similar to photosynthesis, although light is 

 not a direct factor in their formation. Their exact chemical 

 composition is not known, but they are known to be: very com- 

 plex and to contain carbon, hydrogen, oxygen, nitrogen, sulfur, 

 and usually phosphorus. They may be classified in three prin- 

 cipal groups, dependent primarily on their solubility, as follows 1 : 

 (a) the simple vegetable proteins, including the albumins of 

 seeds and cell sap, which are mostly soluble in water; (6) the 



