SOILS FERTILIZERS. 23 



not accompanied by exchange reactions. The maximum specific surface and the 

 maximum susceptibility to thermal influences are found in the upper soil sec- 

 tions in which the colloid formation processes are most intensive, thus showing 

 a specific relation between absorption and the soil colloids. 



On the assumption that the thickness of the water film on the soil par- 

 ticles remains constant, the following conclusions are drawn : The absorp- 

 tive power of the absorbing medium decreases with a decrease in its effective 

 surface. The absorption of calcium in the different layers of chernozem soil 

 depends on the content of calcium which is already absorbed and is displaced by 

 ammonium chlorid solution and not on its total calcium content. The podzol 

 soil, on account of its extremely leached out condition and poverty in absorbed 

 matter, shov.'s a series of concordant results for phosphoric acid as well as for 

 bases. Chernozem, on the other hand, on account of its complex formation, 

 produces a regular series of results only for ammonia. 



Removal of humus by oxidation with acid-free hydrogen peroxid showed that 

 for chernozem, humus, even in the layers rich in it, did not appear to be an 

 exclusive factor of absorption. In podzol soil the decrease in ammonia absorp- 

 tion due to this treatment amounted to 65 per cent of the original amount. 



Influence of radio-activity of the air on exposed drop cultures of micro- 

 organisms, A. Trillat and Fouassier {Compt. Rend. Acad. Sci. [Paris], 159 

 (1914), No. 2.'i, j)i). 817-819) .—It is shown that the growth of cultures of micro- 

 organisms may be influenced to a marked extent by the radio-activity of the 

 atmosphere, and that the latter may vary with the nature of the soil. 



Studies of the microfauna of soils from rice localities, A. Cauda and G. 

 Sangiokgi (Centbl. Bakt. [etc.], 2. AM., ^2 (1914), No. 15-16, pp. 393-398, figs. 

 6). — Studies of the microfauna of different soils and of the same soil under 

 different cultural treatments are reported, and incidentally a comparison of cul- 

 ture media is made. 



It was found that the composition of the culture medium exerted a definite 

 influence on the development of protozoa. With the Omelianski and Giltay solu- 

 tions the development was more marked than with the other solutions used. 

 The development of protozoa began usually on the sixth or eighth day of incu- 

 bation, proceeded until the fourteenth to eighteenth day, and then gradually 

 subsided. The amcebye were the prevailing forms and were present in all 

 cases. In only one case were the flagellates more numerous than the amoeba?, 

 and the flagellates and ciliates were sometimes entirely absent. The different 

 soils showed marked variations in number and kind of protozoa. Soils widely 

 separated but subjected to the same cultural treatment showed the same indi- 

 vidual protozoan development. 



It is thought that, aside from the physical, chemical, geological, and bio- 

 logical factors, certain other factors related to the nature of the vegetation exist 

 in the soil which have a special influence on the vitality of the small-animal life 

 of the soil. 



Contribution to the knowledge of the physiology and distribution of de- 

 nitrifying thiosulphate bacteria, A. Gehring {Centbl. Bakt. [etc.], 2. Abt., 42 

 {1914), No. 15-16, i)p. 402-438) .—The author briefly reviews work of others 

 bearing on the subject, and reports studies of the anaerobic denitrifying sulphur 

 bacteria found by Lieske (E. S. R., 28, p. 35) with reference to their physiology 

 and distribution in soils. 



These bacteria were found in different kinds of silt, in compost, cultivated 



soil, beech forest soil, and upland moor peat. The numbers were constant at 



different depths in peat and cultivated soil but varied greatly in the different 



soils examined, increasing with an increasing carbon content of the soil. Dif- 



96619°— No. 1—15 3 



