272 FIRST YEAR COURSE IN GENERAL SCIENCE 



mals (including man, of course) could not live a generation 

 without green plants, even if there were an abundance of all 

 the elements needed for their growth. Animals cannot make 

 organic matter from inorganic matter. 



Wild cattle, horses, sheep, and deer live mainly upon leaves. 

 Domestic cattle require dried grass to eat in the winter. 

 Wild hogs and bears find their food largely in nuts and roots. 

 These are simply a few illustrations of the need of plants 

 among the large herbivorous animals. Many worms, in- 

 sects, and birds live upon plant food. The waters of the 

 land and of the ocean are rich in plant life (some of it micro- 

 scopic in size) which is food for fishes, corals, and sponges. 

 The carnivorous animals of the land and sea feed upon the 

 herbivorous animals. 



Starch, sugar, fat, and proteid are the food of all kinds of 

 animals. These are the products of the chemical laboratory 

 in the plant. Plants are the food makers of the world. 



306. Digestion. Starch and proteid are foods, but both 

 of them are insoluble in water, and hence need to be digested 

 before they can circulate through the plant. Digestion con- 

 sists in changing foods chemically so that they are soluble. 

 For example, starch is changed to sugar, and then the 

 sugar is dissolved in the water which is present in every 

 part of a growing plant. After this, the dissolved sugar 

 can be transported from the leaves to any living cell of the 

 plant, to be used as a basis for making proteids, for immedi- 

 ate use as food, or for storage against future need. 



307. Storage of Food in Plants. Plants store food for 

 their own use in the root, as the beet does; in the under- 

 ground stem, as the white potato does; or in the base of 

 the leaves, as the onion does. Food for the benefit of a 

 future plant is always stored in the seed. The reason that 

 roots of beets and carrots furnish food for man and animal 

 is that the plant has stored here starch, proteid, and sugar 

 for its own use the next year, when new stems, flowers, and 



