206 



THE ATMOSPHERE 



denitrifying bacteria, and those bacteria which produce the 

 hydrolytic fermentation of urea into ammonium carbonate 

 (CO (NH 2 ) 2 + 2H 2 = C0 3 (NH 4 ) 2 ), &c. 



The discovery of nitrifying bacteria, and of the fact that 

 atmospheric nitrogen is assimilated by their means, is one of 

 the most interesting and important of recent times. 



Beijerinck discovered that a bacterium the bacterium radici- 

 cola lives symbiotically in the root nodules of the Leguminosae, 



Products 

 p/a,nt lifk 



'acts of 

 riaJ 



mpositiofi 

 monia, etc. 



fOIL. 



WATER NIT KATES 

 & OTHER SALTS. 



FIG. 7 



such as the pea, clover, lupin, and that by means of these bacteria 

 the peas acquire more nitrogen than there is in the test soil. 

 Such crops may be grown and ploughed in to enrich sandy soils 

 for wheat growing. Kiihn has calculated that a hectar (about 

 two acres) of soil may be enriched by 66 kg. of N 2 yearly by 

 means of nitrifying bacteria. The raw nitrogenous material avail- 

 able for the synthesis of proteid includes (1) the atmospheric N 2 

 obtained by nitrifying bacteria. (2) The traces of ammonia and 

 nitric acid in the air. Electric discharge in a moist atmosphere, 



