HOW LEGUMES SECURE NITROGEN. 135 



Acquiring of Nitrogen. Leguminous plants have a 

 high nitrogen content. In the farmer's parlance, they 

 make "rich feed." They are rich in protein. Protein is 

 the thing in feeds of which the world is most short. Leg- 

 umes are rich in nitrogen, and nitrogen is commonly de- 

 ficient in soils. Legumes make soils on which they grow 

 rich, particularly when they decay on the land or are 

 turned under. The farmer knew ages ago that clovers, 

 alfalfa and other legumes enriched soils. Within very 

 recent years men have learned how this is done. It seems 

 to be accomplished by means of micro-organisms living 

 on their rootlets or in nodules attached to their roots. 

 There is much to learn about this process. 



How the Nitrogen Is Secured. There is much to be 

 learned yet about how this work is done. So far as we 

 now know this is the way of it: There are probably a 

 number of kinds of bacteria inhabiting leguminous plants. 

 Few if any legumes are without their own especial sort 

 of bacteria, and each sort produces on its host plant a 

 nodule or tubercle. One can find these even on locust 

 trees, on wild legumes, on soybeans, cowpeas and clovers 

 of all sorts. Some men believe that the bacteria inhabit- 

 ing one species will in a little time adapt itself to another 

 species, if that chances to be planted on the soil which 

 it inhabits ; that is, if alfalfa were sown on land filled with 

 red clover-inhabiting bacteria within a few months the 

 bacteria of red clover would learn to grow on alfalfa. My 

 own observation would not at all support this view. 

 True, certain bacteria live on a number of related spe- 

 cies. For example, the same bacteria/so far as we know, 



