CHAPTER XIX 



ORIGIN OF THE CULTIVATED LEGUMES 



Clover • Alfalfa • The lentil • The bean • The pea • The vetch • The lupine • 

 The soy bean • The cowpea 



A certain class of valuable plants is known as legumes. The 

 distinguishing botanical trait of legumes is that they bear their 

 seeds in pods, like peas and beans. The pod may be large and 

 straight as in these familiar species, small and inconspicuous as 

 in clover, or spiral-shaped as in alfalfa. In all cases, however, 

 the seeds, whether large or small, resemble beans in splitting 

 readily into two equal parts, unlike corn or wheat or the seeds 

 of the grasses generally. 



The physiological distinction of leguminous plants is a very 

 peculiar one, and one that is unknown in plants outside this 

 particular family. It is this : there will nearly always be found 

 growing on the roots of all legumes little nodules or warts called 

 tubercles. These tubercles vary in size and shape from those 

 of the red clover, which are not so large as the head of a 

 pin, up to those of the soy bean, which are as large as a 

 small pea. 



These tubercles are really the home of millions of microscopic 

 plants called bacteria, which are parasitic upon the legume ; that 

 is to say, they depend upon the host plant for food, and to 

 that extent they are a disadvantage. This disadvantage is, how- 

 ever, more than offset by their exceeding usefulness in the 

 matter of fertility. 



The agricultural distinction of the legumes generally is that 

 the bacteria within these tubercles have the power of taking the 

 free nitrogen of the air and putting it into combinations that 

 may be used as food for plants generally, a property that is not 



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