180 Report of the Department of Bacteriology of the 



Theoretically, it had been reasoned that bacteria could not make 

 use of congealed water in their physiological activities. Experi- 

 mentally, freezing had been shown to prevent the growth and even- 

 tually to kill some types of bacteria (as for example B. typhosus). 

 Probably these reasons have been largely responsible for the small 

 attention given to the bacterial flora of winter soil. 



HISTORICAL. 



Remy 1 was among the first to furnish information as to the seasonal 

 variation in numbers of bacteria in field soil. His attention, how- 

 ever, was directed mainly toward the physiological functions of the 

 bacteria, and he did not try to perfect his methods of quantitative 

 study. It is perhaps for this reason that he found no great variation 

 in the numbers, and that his highest count was not over 4,000,000 

 per gram. None of Remy's samples were taken during the winter. 



Hiltner and Stormer, 2 in the course of some experiments designed 

 to show the effects of CS 2 -treatment and of fallowing, took samples 

 throughout more than one year. A few of their samples were taken 

 during the winter, but none of them were from soil that had been 

 long frozen. Their highest count was made from soil that had been 

 frozen only a few days before the sample was taken. 



Fabricius and von Feilitzen 3 carried out quantitative studies on 

 five soils throughout one vegetative season. They found that the 

 germ content showed a close relationship to soil temperature, so far 

 as they tested the matter; but they examined no winter samples. 



Kruger and Heinze, 4 in the course of an investigation of fallow 

 soil, took several samples for bacteriological study during one year, 

 omitting the winter. 



Engberding 5 took numerous samples during two seasons of plant 

 growth from fallow and cropped plats, manured and unmanured 

 plats. During most of the year the samples were taken at short 

 intervals; but between October and March only two samples were 

 taken, both of which were from the same plat. These two samples 

 gave moderately high counts, although not so high as some of the 

 others. 



•Remy, Th. Bodenbakteriologische Studien. Centbl. Bakt. Abt. II, 8:657-662, 

 699-705, 728-735, 761-769. 1902. 



2 Hiltner, L., and Stormer, K. Studien liber die Bakterienflora des Ackerbodens, 

 mit besonderer Beriicksichtigung ihres Verhaltens nach einer Behandlung mit 

 Schwefelkohlenstoff und nach Brache. Kaiserliches Gesundheitsamt, Biol. Abt. Land- 

 u.Forstw. 3:445-545. 1903. 



3 Fabricius, O., and von Feilitzen, H. Ueber den Gehalt an Bakterien in jungfrau- 

 lichem und kultiviertem Hochmoorboden auf dem Versuchsfelde des Schwedischen 

 Moorkulturvereins bei Flahult. Centbl. Bakt. Abt. II, 14: 161-168. 1905. 



4 Kruger, W., and Heinze, B. Untersuchungen iiber das Wesen der Brache. 

 Landw. Jahrb. 36: 383-423. 1907. 



5 Engberding, D. Vergleichende Untersuchungen iiber die Bakterienzahl im 

 Ackerboden in ihrer Abhangigkeit von ausseren Einflussen. Centbl. Bakt. Abt. II, 

 23:569-642. 1909. 



