116 EXPERIMENT STATION RECOED. IVol. 3fi 



Measuring biological actions by the freezing-point method directly in the 

 soil, G. J. BouYoucos {Science, n. ser., 44 {1916}, No. 1124, PP- 65, 66). — Ex- 

 periments conducted at the Michigan Experiment Station on the influence of 

 the decomposition of dried blood, cottonseed meal, and animal tankage in soils 

 on the concentration of the soil solution as indicated by depression in the freez- 

 ing point are reported. The fertilizers were added at the rates of 0.5 and 1 gm. 

 per 800 gm. of soil. 



It was found that " the decomposition of these nitrogeneous materials 

 increased tlie depression, and hence the concentration, of the soil solution 

 markedly, and the magnitude of the increase seems to vary with the nature of 

 the material and quantity employed. In some other experiments the amounts 

 of these nitrogenous materials were used, not in equivalent weight but in 

 equivalent nitrogen content, and the freezing-point depression was measured 

 at various intervals. The results show that dried blood reached its maximum 

 decomposition first, followed by animal tankage and cottonseed meal, respec- 

 tively. . . . 



" It appears that the freezing-point method may be used to great advantage 

 in making comparative studies of tlie decomposibility of various organic sub- 

 stances in the same kind of soil, or the decomposing power of different classes 

 of soil on the same organic substance, or of the same soil differently treated, 

 etc." 



Effect of grinding soil on the number of micro-organisms, E. B. Fred 

 {Science, n. set:, 44 {1916), No. 1130. pp. 282, 285).— Tests with silt loam, clay, 

 sand, silt clay loam, sandy loam, medium sand, loam, muck, and garden soils 

 to determine the influence of grinding on the number of micro-organisms showed 

 that " grinding greatly reduced the number of bacteria except in silt loam. 

 Apparently the greatest injury caused by grinding for one hour is noted in the 

 case of sandy soils. When the soils were ground for 8 or 24 hours, there was 

 an enormous decrease in the bacterial flora. . . . After 24 hours of grinding 

 the soil was rendered almest free of bacteria. . . . 



" Dilution counts on various culture solutions adapted to protozoa showed 

 that the unground soils contained protozoa in dilutions greater than 1 to 10.000, 

 while in many cases tlie ground soil failed to show any growth of protozoa. 

 The garden soil contained protozoa in the first dilution, 1 gm. in 10 cc. of the 

 medium. When ground for 24 hours this same soil did not show the presence 

 of protozoa. 



" From the results, it seems fair to conclude that grinding soil in a ball 

 mill injures the soil micro-organisms. If this process is continued for several 

 hours, the soil will be partially sterilized." 



The gases of swamp rice soils. — III, A hydrogen-oxidizing bacterium 

 from these soils, W. H. Harrison and P. A. Subramania Aiyer {Mem. Dept. 

 Agr. India, Chem. Ser., 4 {1916), No. 4, pp. 135-148, fig. i).— Continuing work 

 previously noted (E. S, R., 33, p. 216), further studies were made on the bac- 

 teria in the film on the surface of swamp-rice soils, which had previously 

 shown the ability to oxidize hydrogen. 



Cultivation of a crude cixlture in Kaserer's medium (E, S. R., 18, p. 1028) 

 under autotropic conditions and incubation in an atmosphere consisting of a 

 mixture of carbon dioxid, methan, oxygen, and hydrogen yielded a culture 

 composed of a mixture of two species of bacteria, one nonmotile and the other 

 smaller. Further cultivation of the mixed culture in the medium to which 

 organic matter was added led to the conclusion that the particular bacterium 

 which was able to oxidize hydrogen was unable to exist in pure culture under 

 autotropic conditions. " The mixed culture was plated out on mineral agar, 

 to which 0.1 per cent sodium asparaginate had been added, and incubated in 



