CHAPTER I. — THE CELL. 



137 



plants, and which not infrequently occurs, also, in other fruits, 

 and tartaric acid (H 6 C 4 6 ), which exists in considerable quantity 

 in grapes, but is not Wanting in many other fruits. Many other 

 acids, however, occur less abundantly. Among them may be 



Fig. 380. 



Fig. 381. 



Fig. 382. 



Fig. 380. — Curcuma starch. Magnified about 200 diameters. 

 Fig. 381.— Oat starch. Magnified about 375 diameters. 

 Fig. 382.— Bean starch. Magnified about 375 diameters. 



mentioned acetic, formic, benzoic, cinnamic, gallic, butyric, 

 valerianic, angelic, succinic, succinamic, and the fatty acids. 

 Chemically, they differ much among themselves, some being 

 highly complex, others comparatively simple ; some are quite 

 stable, while, others are 

 readily decomposable. 

 They also differ much in 

 their relations to the vital 

 processes in the plant, 

 some performing impor- 

 tant functions, while 

 others must be regarded 

 as purely waste products. 

 They may exist free or in 

 combination with various 

 bases. The acid reaction 

 which many plants ex- 

 hibit may be due either to the presence of free acids, or to acid 

 salts in solution. 



Fixed Oils or Fats. These occur in the cells of various 

 parts of plants, but are particularly abundant in certain fruits, as 

 that of the olive, and in many seeds. In the latter instance, 



Fig. 383.— Cells from root of Dahlia mat have 

 been treated with absolute alcohol to precipitate the 

 inulin. This is seen in the cells in the form of 

 sphere-crystals. Magnified about 250 diameters. 



