The Plan I. 99 



Camphors are obtained by the distillation of certain tropical 

 woods. They differ from terpenes in containing oxygen added 

 to the elements of the latter. The two classes of compounds are 

 apparently closely related products of the chemical processes of 

 the plant. 



Eesins occur in pitches and are closely allied in composition to 

 the camphors. Like terpenes and camphors they may be distin- 

 guished from fats by failure to produce soaps by the usual 

 process of saponification. 



Organic acids often occur in plants in considerable amounts 

 and are responsible for the sour taste frequently observed. They 

 are produced by the fermentation of carbohydrates and rarely 

 occur free but usually as acid or neutral salts of potassium or 

 calcium. The sourness of lemons is due to critic acid. The acid- 

 potassium salt of oxalic acid occurs in sorrel and acid-calcium 

 oxalate has been found in rhubarb. Malic acid is common in 

 1'ruits, and exists as the acid-potassium salt in rhubarb and the 

 acid-calcium salt in the berries of the mountain ash, tobacco 

 leaves and other plants. The acid-potassium salt of tartaric 

 acid is characteristic of the grape, and potassium and calcium 

 salts of this acid are found in the pine-apple, sumac berry and 

 other fruits. It is interesting to note in this connection that 

 lactic acid develops in corn silage as a product of hydrolysis of 

 dextrose and other carbohydrates. These acid compounds play 

 an important part in the production of characteristic flavors. 



The proteins are compounds of the greatest importance in the 

 plant. They are of complex structure, containing not only car- 

 bon, hydrogen and oxygen, but also nitrogen and sulphur. This 

 large number of constituents makes possible a variety and com- 

 plexity of structure fitting them for the delicate and complicated 

 reactions which characterize life processes. Proteins form the 

 basis of the life-bearing protoplasm and nucleus of each plant 

 cell. Although contained in every cell, they are localized chiefly 

 in the seed and furnish nitrogen for the first protein structures 

 of the seedling. Individual proteins are characterized by a con- 



