258 DOMESTICATED ANIMALS AND PLANTS 



possessed, so far as we know, by any other form of life. When 

 the student comes to realize, by the study of the fertility problem, 

 the difficulty encountered by farmers in getting sufficient nitro- 

 gen into the soil for profitable growth of crops, then the real 

 value of legumes as the only natural and cheap source of nitrogen 

 will be fully appreciated. 1 



The nutritive significance of legumes lies in the high nitrogen 

 and mineral content of both the grain and the stem. As the 

 grasses are notable for their carbon content in the form of either 

 starch or oil, so the legumes are remarkable for their nitrogen 

 and mineral content, especially the former. The exceeding 

 rarity of nitrogen gives it a high value for animal food as well 

 as for fertility, all of which goes to make the legumes, agricul- 

 turally speaking, the most distinctive family of plants ever do- 

 mesticated. 2 They make an ideal food for growing animals and 

 a fair substitute for meat in the diet of man ; indeed, wherever 

 in the earth man has lived with little or no flesh food he has 

 drawn the more heavily upon the seeds of legumes. 



Clover. Under this general name are grouped a variety of 

 species more or less closely related. 



1. Trifolium pratense, the common red clover, sometimes 

 called purple clover or meadow trefoil, the latter from its three- 

 parted leaf. 



1 Nitrogen costs in the markets, in the form of commercial fertilizers, ap- 

 proximately fifteen cents a pound everywhere, but can be produced by legumes 

 in the proper rotation for next to nothing. 



2 It is sometimes necessary to " inoculate " for the growth of legumes ; that 

 is, to apply the proper bacteria. The bacteria are not the same for different 

 species of legumes. For example, the clover tubercle will not develop on the 

 alfalfa nor that of the pea upon the bean. If the particular species, say alfalfa, 

 has never before been grown in a locality, its specific bacteria will likely not 

 be present, in which case the tubercles will not form and no nitrogen will be 

 taken from the air, such a plant becoming a heavy nitrogen consumer instead 

 of a nitrogen producer. Inoculation then becomes necessary, for if the tuber- 

 cles do not form, the legume is very exhaustive to land instead of benefiting 

 it, and ultimately itself dies of nitrogen starvation. Inoculation is generally 

 effected by scattering over the surface a little soil taken from a field in which 

 the same legume has grown with well-developed tubercles. One to one and a 

 half bushels per acre is sufficient if evenly applied. 



