FOOD FOR LIVE STOCK 41 



adequate amount of protein in the grains, chiefly 

 oats, that are fed them. 



Cattle that are being fattened may thrive as 

 well on foods that are less rich in protein. 



Milch cattle, and growing cattle, on the other 

 hand, need a nitrogenous diet. And, indeed, all 

 along the line, it is not to be denied that a protein 

 food has exceptional nutritive value. It is partly 

 at least with this in mind that the intelligent 

 agriculturist mixes clover with the timothy in 

 his pastures and in his hayfield. 



At least a partial explanation of the high nitro- 

 gen content of the leguminous plants has been 

 furnished by the discovery that these plants have 

 the very unusual capacity to extract nitrogen 

 from the air. Most plants, as we have seen, are 

 ' quite powerless to take even the most infinitesimal 

 quantity of nitrogen from the air, and would 

 starve to death for lack of nitrogen even while 

 their tissues are perpetually bathed in it as the 

 tissues of all aerial plants necessarily are inas- 

 much as the atmosphere contains nitrogen as its 

 most abundant element. 



But the leguminous plants are able to extract 

 nitrogen from the air directly; not, however, with 

 the aid of their leaves or stems, but only by way 

 of the roots, and there only with the aid of the 

 little tubercles that develop under the influence 



