DECOMPOSITION OF ORGANIC MATTER IN THE SOIL. 257 



ability to produce ammonia out of egg albumen. The following propor- 

 tions of the protein nitrogen were converted into ammonia in twenty days: 



B. mycoides ............ 46 per cent. B. suUilis ................ 23 per cent. 



B. (Proteus') -vulgar is ... 36 per cent. B. janthinus ............... 23 per cent. 



B. mesentericus vulgatus. 29 per cent. B. fluorescens putidus ...... 22 per cent. 



Sarcina lutea .......... 27 per cent. B. fluorescens liquefaciens . . . 16 per cent. 



Furthermore, apart from the variations from species to species, differ- 

 ences have been observed by Marchal and many other investigators 

 between one strain and another of any single species isolated from the same 

 or different soils. It must be remembered, therefore, that in the study 

 of ammonincation in soils and culture solutions, due consideration should 

 be given to differences in physiological efficiency as they are manifested by 

 strains and species of microorganisms. 



Apart from the ammonifying bacteria already mentioned there is a 

 group of organisms studied by Miiller, Pasteur, van Tieghem, Leube, 

 Miquel, Beyerinck and others. These are the so-called urea bacteria, 

 capable of intensive transformation of urea and allied compounds into 

 ammonium carbonate, by means of the enzyme urease. 



NH 



2 H 2 O=(NH 4 ) 2 CO 3 



I 

 NH 2 



Morphologically these organisms include spherical and rod forms, 

 spore-bearing and non-spore bearing species. Most of the urea bacteria 

 are particularly prominent in the transformation of animal manures. 



NITRIFICATION. Experimental Study. The term nitrification refers 

 to the oxidation either of ammonia or of nitrites to nitrates. In a broader 

 sense nitrification may be defined as the production of nitrates from 

 decomposing organic matter. Saltpeter or niter, the terms formerly 

 applied to potassium nitrate, possessed, for a long time, a peculiar interest 

 because of its relation to gunpowder. Whether it be true or not that gun- 

 powder was known to the Chinese before the beginning of the present era, 

 there is no doubt that for several centuries it played an important part 

 in the political and economic history of Europe. The large quantities of 

 gunpowder consumed in the almost incessant wars created a steady 

 demand for saltpeter that was not readily met by the saltpeter refiners of 

 India, Hungary and Poland. European nations, particularly France, 



