1914] Lipman-Burgess : Ammonification in Sails hy Pure Cultures 147 



series are relatively so small that the margin allowable for safe 

 comparison must of necessity be much decreased and therefore 

 comparisons are more difficult. 



Clay- Adobe Soil 



Passing on to a study of the data obtained with the clay-adobe 

 soil as a medium, we find again that he physical condition of the 

 soil is a powerful factor in determining the amount of ammonia 

 produced in soils by pure cultures of organisms possessed of 

 ammonifying powers, if the fifteen different organisms used are 

 a suitable criterion. This confirms the findings of J. G. Lipman 

 in his long series of ammonification experiments with mixed cul- 

 tures. For practical purposes, we may add that most of the 

 bacteria ammonify dried-blood nitrogen equally well in the clay- 

 adobe soil and in clay-loam soil, though there does appear to be 

 a slight though consistently greater amount of ammonia produced 

 in the first-named soil. Again, we find in the clay-adobe soil 

 an organism which stands out as far superior to all others in 

 ammonifying efficiency and again also it is not the same organism 

 as manifested that superiority in the preceding soil. Wliile the 

 duplicate determinations here do not agree as well as might be 

 desired, they indicate amounts so much greater than the quan- 

 tities of ammonia produced by the other organisms of the series 

 that there can be no doubt of the marked and superior efficiency 

 of B. tumescens as an ammonia producer from the nitrogen of 

 dried blood in the clay adobe soil as a medium. Two other 

 organisms appear to be in the second class in this series and they 

 are Mic. tetragenus and B. mycoides. The first, it can be seen 

 from Table III, occupied third place in efficiency in the clay 

 loam soil, but the second has thus far been relatively inefficient. 

 All the other organisms of the series do not manifest differences 

 in efficiency of sufficient magnitude to warrant further comment, 

 except that it is curious and interesting to note that the most 

 efficient organism in the sandy soil is the least efficient organism 

 in the adobe soil. 



It should be remarked here that the generally excellent agree- 

 ment between duplicate determinations, as shown in the table. 



