SOIL PHYSICS, CHEMISTRY AXD IkHCROBIOLOGY 94I 



partly due to the hygroscopic moisture retained by such soil. This is, 

 however, not the only factor in operation, the survival of bacteria in a 

 soil not being directly proportional to the size of its particles and its 

 hygroscopic moisture. 



(2) The bacteria under experiment survive drying in rich garden loam 

 longer than in sand. 



(3) If, before being subjected to drying in sand, the bacteria are sus- 

 pended in a watery solution of the said soil, they survive longer than if 

 such suspension were effected in a physiological salt solution. 



(4) The watery solution of the said garden soil therefore must con- 

 tain substances exerting a protective effect on the bacteria dried. 



731 - New Russian Studies of Nitrogen- flxing Bacteria. — i. omelianskij \'. i,. and 



SoLTJXSKOV >I. Sar la distribution des bacteries fixatrices d'azote dans les sols russes (On 

 the Distribution of Nitrogen- fixing Bacteria in Russian soils) in Archives des Sciences bio- 

 loiiques publiees par V Institiit imperial de medecine experimentale a Petrograd (French Edi- 

 tion), Vol. X\nil, No. 5, pp. 459-482, 3 plates. Petrograd, 1915. — II. Ojmelianskij V. I,., 

 Fixation de I'azote atniospherique au moj^eu des cultures mixtes (Fixation of Atmosphe- 

 ric Nitrogen by Mixed Cultures), Ibid., Vol. X\ail, No. 4, pp. 338-377, i fflate. Petro- 

 grad, 1915. — III. Ojieli.\nskij V. 1,., Sur les rapports entre la fixation de I'azote et la 

 consominatiou de matieres organiques non azotees par les bacteries fixatrices d'azote. 

 (On the Relations between Fixation of Nitrogen and the Consumption of Non-nitrogenous 

 Organic Substances by Nitrogen-fixing Bacteria). Ibid., Vol. XVIII, No. 4, pp. 327-337, 

 2 fig. Petrograd, 1915. — IV. Omelianskij V. I,., Sur la physiologic et la biologic des 

 bacteries fixatrices d'azote (The Physiology and lyife Historj' of Nitrogen-fixing Bacteria), 

 Ibid., Vol. XIX, No. 2, pp. 162-208, I plate. Petrograd, 1915. 



I. Distribution of Nitrogen- fixing Bacteria in Russian Soils. M. Ome- 

 lianskij and Mlle Solunskov start out from the principle that the universal 

 occurrence of a given micro-organism with clearly defined chemical func- 

 tions is one of the most conclusive arguments as to the importance of such 

 micro-organism. The\^ give the results of their enquiries caried out in the 

 General Microbiology Section of the Imperial Institute of Experimental 

 Medicine in Petrograd, on the occurrence of Clostridium Pasteurianum, an 

 anaerobic nitrogen-fixing bacterium, and Azotohacter chroococcum, an aero- 

 bic nitrogen-fixing bacterium, in the soil of the Russian Empire. The 

 investigations were made on soils taken frcm dift'erent depths in 12 locali- 

 ties of European and Asiatic Russia. Besides these, the presence of Clo- 

 stridium Pasteurianum only was studied in 14 samples from other localities 

 of the Empire. The results were as follows : 



(i) Azotohacter and Clostridium Pasteurianum occur very widely in 

 soils of different characters and in the most divergent regions of the Empire. 

 In some few cases only the nitrogen-fixing agent was isolated, for instance 

 Azotohacter in the sands of the Kirghese steppes and in the peat soils in the 

 north of European Russia (province of Archangel). 



(2) The races of Azotohacter and Clostridium Pasteurianum isolated 

 in the enquiries are clearly morphologically distinct, especially those of Clo- 

 stridium Pasteurianum. 



(3) In these experiments, the two bacteria .studied exhibited a dif- 

 ferent fixing power, weaker in Azotohacter th.2in\nClostridiuinPasteuriamtm, 



