RECLAIMING LOST NITROGEN 141 



declare such to be the case, some even insist that other 

 plants besides the legumes have the power of nitrogen 

 fixation. They say that some plants other than legumes 

 fix nitrogen to a slight degree, only, still they have the 

 power. If this theory is correct, it will lead, doubtless, 

 to still greater helpfulness in maintaining the fertility 

 of the land. 



A third view of nitrogen fixation is this : Some bacteria 

 in the soil just what kind we do not know seize on 

 the nitrogen as it moves about in the soil with the air 

 and hold it fast, by placing it in some compound unas- 

 similable as plant food. A second step is then made : 

 legumes and tubercle bacteria couple their efforts and 

 nitrogen passes into a state that plants can use. It is 

 fixed nitrogen : it is real, usable plant food. 



The symbiotic theory finds a larger coterie of advo- 

 cates. It is the theory of mutual helpfulness : the legume 

 helps the bacteria by furnishing carbohydrates and dwell- 

 ing places for them : the bacteria help the legume by 

 furnishing nitrogen as rapidly as it is needed for all uses 

 of the plant. This theory renders each party dependent 

 upon the other: without a legume there is no dwelling 

 place for bacteria and without the bacteria there is no 

 nitrogen for vigorous growth and abundant fruit for the 

 legume plant. Hence, this is a theory of cooperation, of 

 harmonious mutual service: one helps the other; both 

 are materially bettered because of the other. 



The point that is important. We need not concern our- 

 selves particularly about these theories. The best plan 

 is to leave them to the scientist, who sooner or later will 

 clear up the matter. Nor does it matter. The good work 

 will go on just /the same: legumes and bacteria will con- 

 tinue to add the fat to the land ; they will continue to 

 enrich the farm ; they will continue to do this work 



