METABOLISM— DIGESTION— TRANSLOCATION— GROWTH 211 



food materials, the absorption of sunlight, the manufacture 

 and translocation of the true food compounds, the trans- 

 formation of compounds from one form to another, the making 

 of the various plant products, and growth — all involve cata- 

 bolism. Therefore, we find numerous waste products ; i.e.j waste, 

 so far as the plant is concerned, although many of them are of 

 commercial value. They are the gases and water which are 

 given off by the plant ; the bark, leaves and twigs which are shed 

 by the plant, and many other materials. 



Digestion. — This is the changing of the true food materials 

 into soluble products. All food materials must be digested by 

 the plant before they can be moved from place to place or used 

 for growth or repair. In some cases the plant may use the food 

 as soon as it is formed, but' in most cases it uses the foods which 

 have been stored up for this purpose. The plant has no stomach 

 or other specialized organ for digestion, but the work of digestion 

 is carried on in the cells and is most prominent in the germina- 

 tion of seeds, tubers and bulbs and in all new growths. These 

 organs serve for the accumulation or storage of insoluble starches 

 and other food materials which must undergo a digestion in 

 order to render them soluble. In this soluble form they are 

 transmitted to the various parts of the plant and used in the 

 processes of growth. 



The digestion is very generally accomplished by means of 

 ferments or enzymes which are produced by the living proto- 

 plasm, and are of the same character as those produced by the 

 animal. In fact, the chemical processes of digestion are prac- 

 tically the same in the plant as in the animal. These enzym.es 

 are nitrogenous bodies, and there are no doubt many different 

 kinds which act on many different kinds of plant products. 



