BuEEAu OF Agkicultuee. 241 



bean and cpw pea fumisla andustrious insects mueili 

 forage at times. 



For hay and for grazing, the clovers have a value 

 everywhere. As feed they rank higher than the grasses, 

 though too concentrated for steady feeding alone. Mixed 

 with grasses they furnish as good a ration as can be 

 provided. 



The seeds of many members of the group, such as 

 the peas and beans, furnish a very nutritious food for 

 man, the soy bean, for example, providing to the 

 Japanese a variety of dishes, and furnishing beside much 

 of the fodder used for stock in Japan. 



But while we should find it difficult to do without 

 this source of food and feed, we could let it go rather 

 than lose the grasses, were it not for a very remark- 

 able peculiarity of the clovers and beans. 



Most of them, and probably all, can get nitrogen 

 from the air, and as the true grasses cannot, the latter 

 are dependent on plants of the clover family and on man 

 for this absolutely necessary plant food. The story of 

 how clovers get nitrogen and leave it in the soil for other 

 plants is one of the most curious known to science and 

 to agriculture. 



If one of these plants is taken up carefully, so as 

 not to lose many of the fibrous roots, little round, or oval, 

 knots, commonly styled nodules, will be found attached 

 to the roots, and sometimes to the bases of the plants 

 themselves. Under the microscope these knots are found 

 to contain numerous minute germs or bacteria, and these 

 are known to be the cause of the knots, and also the 

 means by which the nitrogen is picked up from air 

 in the soil. 



Now nitrogen is a very costly fertilizing material, 

 and yet the farmer has it in his power to get it simply by 

 growing a clover or bean crop. The value of these 

 plants in enriching soil was long known before the ex- 

 planation of it was furnished. Since the secret was 

 learned it has been found possible to inoculate soUs in 

 which the nodules do not occur and thus enable plants of 

 the clover family to do their office there as nitrogen 

 gatherers. Unless the bacteria are present, clovers ex- 



