132 AGRICULTURAL BACTERIOLOGY 



gen content of the aerial parts of the plants bearing nodules 

 is higher than plants on which nodules are not present. 

 The composition of non-legumes growing with legumes is 

 also changed in the same manner. 



A few non-leguminous plants may bear nodules on the 

 roots, and apparently have the same relation to free nitro- 

 gen as do the legumes. The most important of these are 

 the alders. The development of the nodules is very sparse, 

 as a rule. 



The legume furnishes the cheapest way of preventing the 

 rapid reduction of the nitrogen content of the soil. Where 

 sandy lands are to be reclaimed and worn-out soils restored, 

 the legume is to be considered a most important factor. 

 The nitrogen thus added to the soil is estimated to cost 

 only from one half to five cents a pound, as opposed to the 

 usual commercial price which is from 25 to 30 cents. 



