AGRICULTURE AND RURAL ECONOMY. 361 



did experimentalists begin to purify the air that they used 

 in repeating Schonbein's experiments than the production 

 of nitrite of ammonia suddenly stopped." 



Concerning: the combination of ozone with free nitrogen 

 in presence of bases, (5), in experiments by Berthelot, ozone 

 prepared from oxygen by the electric discharge did not ox- 

 idize nitrogen in presence of chemically pure baryta water; 

 but air ozonized by phosphorus yielded a trace of nitrate. 

 If the phosphorus was free from nitrogen, the oxidation of 

 free nitrogen by ozone in presence of bases would thus seem 

 to be established (Comptes JRendus, lxxxiv., 61). 



Is the Combined Mtrogeu of the Air the Source of the Assimilated 



Nitrogen ? 



It so happens that plants which gather, or are supposed 

 to gather, nitrogen most readily, as root crops (turnips and 

 the like) and leguminous crops (beans, pease, clover, etc.), 

 have obviously a different foliage from the gramineous crops 

 (wheat, barley, oats, etc.), which are supposed to gather it 

 less easily. It has been commonly taught that the "broad- 

 leaved crops," as the former are designated, have a power of 

 taking nitrogen from the atmosphere in some manner which 

 other crops possess in less degree, if at all. Dr. Gilbert op- 

 poses this view very decidedly: "It may be safely asserted 

 that neither direct experimental evidence nor a considera- 

 tion of the physics of the subject would lead to the conclu- 

 sion that the plants which assimilate more nitrogen over a 

 given area than others do so by virtue of a greater power 

 of absorbing from the atmosphere by their leaves combined 

 nitrogen in the form of ammonia." It is worthy of notice 

 that A. Mayer, w r hose experiments are cited in- support of 

 the theory referred to, says himself that "this hypothesis 

 rests more upon practical experience than upon exact ex- 

 perimental testimony," and accepts it to only a very lim- 

 ited degree. 



The supposed means by which plants might prepare for 

 themselves, or get already prepared, and absorb through 

 their leaves compounds formed from the free nitrogen of 

 the air, would thus seem probably limited to one. 



Q 



