FROM THE AIR BY THE LEGUMINOS^ I7 



it was thought that by reason of their larger foHage and 

 general growth the}- were better able than the Graminese to 

 store up and utilize the small traces of nitrogen existing in 

 combination in the atmosphere. 



Further, it was asserted that the powerful root-system, 

 penetrating deep into the soil, was able to draw up nitrogen 

 from the deeper layers, which was inaccessible to other 

 plants. 



The fourth theory leads us to believe that the very life 

 of the Leguminosai involved the building up and preserva- 

 tion of certain nitrogenous combinations. 



The tinal conclusion attributed to the Leguminosse the 

 unique faculty of assimilating atmospheric nitrogen. 



The tirst and the last theories were refuted by Bous- 

 singault, Lawes, Gilbert, Pugh, and others. The second 

 statement was disproved by the experiments of Mayer on 

 wheat and those of Schloesing on tobacco. These scientists 

 proved that the plants mentioned have the faculty of absorb- 

 ing ammonia by means of their foliage and of assimilating 

 it to a much greater extent than peas and beans. 



The theory based on the greater depth tapped by the 

 root-system was no longer tenable after it was proved that 

 oats and barlev have roots just as well developed as those 

 of peas. 



The fourth hypothesis was the one which found greatest 

 support. Among the supporters of this latter hypothesis 

 we find Heinrich and others stating that the soil has the 

 property of fixing the traces of nitrogen in combination in 

 the air, and it is a matter of general knowledge that dust 

 particles in the atmosphere, and rain as well, always con- 

 tain a more than negligible amount of ammonia and nitric 

 acid. 



Schonbein, Bottcher, Gorup Bezanez, and Ufifelman 

 proved that by the evaporation of water, ammonia was con- 

 verted, at the expense of the primary free atmospheric 

 nitrogen, into nitrous and nitric acid. 



