FEEDING FARM ANIMALS 



Carbon, a principal substance of plants and animals. 

 It is found in soil and air. Animals give it off 

 in breathing and plants take it in through 

 their leaves. United with oxygen it makes 

 carbon dioxide of the air, the principal source 

 for plants to get their supply. 



Nitrogen, a gas in its free state. Both plants and 

 animals require it, and four-fifths of the air is 

 composed of it. 



Elements are 

 Unite d. F e w of 

 these elements ex- 

 ist in the soil in a 

 free state. Two or 

 more have united. 

 In this association 

 they exist as com- 

 pounds. Thus nitro- 

 gen, potassium and 

 oxygen united form 

 potassium nitrate 

 (KNO 3 ) ; and hydro- 

 g e n and oxygen 

 united form water 

 (H 2 O). So, through- 

 out the world, various combinations of these ele- 

 ments are found and are known as chemical com- 

 pounds. 



Cycle of Life. The elements here described as 

 essential to plant growth are needed by animals also. 

 But animals neither can gather them from the soil 

 and the air, nor would it be possible for animals to 



STOMATA, OR LEAF MOUTHS 

 As seen under the microscope on the 

 underside of the leaf. Carbon through 

 the stomata is admitted to the plants in 

 the form of carbon dioxide or carbonic 

 acid gas. 



