CHAPTER VII 

 THE COMPOSITION OF PLANTS AND ANIMALS 



The plant as a source of food is of great interest to feeders 

 of live stock. All our farm animals eat green plants with 

 relish, just as a man enjoys celery. When plants are prop- 

 erly dried and cured as hay, their value for feed is not 

 thereby affected. All our grains are products of plants; and 

 from these directly, or indirectly by milling, we obtain some 

 of our most valuable feeds for farm animals. So the facts 

 are that the plant, in one form or another, really furnishes 

 our horses, cattle, sheep, swine, and poultry with about all 

 the food necessary for growth and production. 



The material of which plants are made is taken from 

 both soil and air, but largely from the soil. Like animals, 

 plants must have food. Chemists say that all matter is com- 

 posed of elements, about thirteen of which provide food for 

 the plants. The names of some of these are common, such 

 as iron, sulphur, and phosphorus. There are four others: 

 carbon, hydrogen, oxygen, and nitrogen that are also impor- 

 tant. Besides these, the plant needs potassium, calcium, 

 sodium, magnesium, chlorine, and silica. Most of these ele- 

 ments are found in different combinations in the soil, more 

 or less dissolved in the water. By means of its roots, the 

 plant takes up the water and so carries this food through all 

 its various parts. As this water or sap moves through the 

 structure of the plant cells, the food in solution is used to 

 promote growth. Carbon, oxygen, hydrogen, and nitrogen 

 are gases in the air. The first two of these unite to form 

 carbon dioxide, or carbonic acid gas, which the plant breathes 

 in through the pores of the leaves. This gas in the plant 

 goes through a change, and the oxygen is breathed out, and 



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