CHEMICAL CHANGES 



227 



Further, the plant absorbs the bacteria, and they disappear. 

 (3) Nobbe and Hiltner found that the stronger the plant, the 

 greater the resistance it offers to inoculation, and the sooner the 

 nodules are emptied. 



Exactly how the nitrogen is transferred from bacteria to plant 

 is not known. 



Inoculation of Legumes. When a legume is planted in new 

 localities, the bacteria suitable to it may not be present to aid it 



Fig. 54. Showing difference in the growth of alfalfa caused by 

 inoculation with bacteria. Illinois Station. 



in the assimilation of nitrogen. The safest plan is to inoculate 

 the soil with the proper bacteria. There are two methods of doing 

 this. 



(i) The first method consists in inoculating with soil from a 

 field where the plants have been growing well. This is the surest 

 method, but open to some objections. Freight charges on the 

 soil may be expensive ; the soil may be difficult to secure ; injurious 

 insects or diseases or weeds are likely to be brought into the soil. 



