12 THE OLIVER PLOW BOOK 



the assimilation, the excretion of water, and breathing. 

 The functions of the leaves in these four processes in- 

 volve a very complicated chemical process which is not 

 very thoroughly understood and does not need to be 

 from a practical standpoint. 



The only thing necessary to know is that a plant, to 

 flower and produce the proper grain, must have an 

 abundance of moisture in order that the sunlight and 

 air may supply the proper gases and heat necessary to 

 bring about these chemical changes. The task of the 

 farmer is to see that air, water and the proper plant food 

 elements are properly proportioned in the soil. He need 

 not worry about the part that surface air plays in the 

 growing of the plants because it is beyond his control. 

 Nature always supplies it abundantly on and above the 

 earth's surface. To be of the utmost value air must be 

 permitted to permeate every particle of the seed bed. 



The tiller of the soil must see that the proper amount 

 of plant food is supplied during the plant's life so that 

 the entire plant can perform its functions. He must 

 not forget also that a plant, even as any animal, can 

 gorge itself so that one part of it will grow to the detri- 

 ment of another. 



The plant may be considered in part as its own food 

 manufacturing establishment; that is, certain of the food 

 elements coming from the soil are mingled with the 

 gases which come through the leaves in such a way as to 

 form the starchy substances of the plants. It is vitally 

 necessary, therefore, that both the soil and air supply 

 the proper elements for these processes to take place in 

 the plant. 



The amount of plant food contained in water is very 

 small, hence, the plant must consume an immense 



