144 University of California Publications in Agricult%iral Sciences [Vol. 1 



The pure cultures of the organisms employed in these investi- 

 gations were obtained by one of us from the bacteriological 

 laboratories of the University of Illinois. Fresh strains of 

 B. suhtilis and B. mycoides were, however, isolated by us from 

 California soils in order to check the stock cultures of the same 

 organisms. The same relative powers of producing ammonia 

 were, however, found to obtain with the fresh as with the old, 

 and different strains thus strengthening the validity of the 

 results below discussed. 



Series I. Experiments with Dried Blood 

 Sandy Soil 



Two per cent of finely sifted dried blood was added to the 

 soils in this series, or one gram per fifty grams of soil. In the 

 case of the sandy soil three series in duplicate were tried, and the 

 same relation under different conditions having been found to 

 obtain between the ammonifying powers of the different organ- 

 isms, we give only one duplicate set of the determinations. The 

 incubation period was twelve days throughout at a temperature 

 varying between 27° C and 30° C. The results of the ammoni- 

 fication determinations with all the soils using dried blood 

 throughout are given in Table III. The percentage of nitrogen 

 of the total amount added which is made available is also given 

 in every case. 



The data in Table III most strikingly indicate the superiority 

 of Ps. putida, B. vulgaris and Sarcina lutea to all other organisms 

 in their efficiency at the production of ammonia from the nitrogen 

 of dried blood. The next fact of singular interest is that B. 

 mycoides, which has, in the hands of several investigators, shown 

 such marked superiority over other ammonifying organisms in 

 the production of ammonia from organic nitrogen in solutions, 

 manifests a relatively low power to transform the nitrogen of 

 dried blood in soil cultures into ammonia. This, moreover, 

 cannot be considered accidental, since different strains of B. 

 mycoides, as above explained, exhibited that same lack of vigor in 

 three duplicate sets of cultures run at different times and under 

 slightly varying conditions of temperature and period of incuba- 



