[vanderleck] bacteria OF FROZEN SOILS 17 



showed a distinct retardation of bacterial growth when in a frozen 

 condition. 

 3. The bacterial flora was more or less the same during the fall, 

 winter and spring, with the exception that after heavy frosts 

 the small transparent colonies characteristic of water and of 

 deeper soils formed a larger proportion of the growth on the 

 plates. 



From these results it seems reasonable to conclude that ordinary- 

 soil bacteria undoubtedly withstand cold to a marked degree, 

 even to temperatures as low as 4° C. or more below zero. The 

 increase in numbers, however, seems to be due to mechanical 

 transportation by moisture coming up from below during heavy 

 frost, and where such transportation is not possible there is an 

 actual retardation in growth as compared with that in unfrozen 

 soils." 



The investigators mentioned above conducted their experiments 

 under moderate temperature conditions and it was questionable 

 whether the same results would be obtained in the more rigorous 

 climate of a Quebec winter. During the winters of 1914-1916 the 

 writer analysed many samples of frozen soils, but during the winters 

 of 1914-15 and 1915-16 the weather was so changeable that no 

 definite plan of research could be adhered to. The winter of 1916-17 

 presented more favorable conditions. From the middle of December 

 until the middle of March severe frost was experienced without any 

 thaw. Occasionally severe snowstorms prevented sampling on account 

 of drifting snow. Five experiments were carried out simultaneously: 



1. Quantitative determination of bacteria in the soil from a cultivated 



field. The soil consisted of a light rich loam to a depth of 18 

 inches and was free from stones. In the fall cabbages were 

 harvested from this field, which was subsequently manured and 

 plowed. 



2. Quantitative determination of bacteria from soil beneath a lawn. 



The sod was about six years old and the soil was very poor and 

 gravelly. On this lawn a plot of about 400 square feet was cleared 

 of snow on the 8th of February, and kept clear until the 24th 

 of February, on which date it was covered over with a heavy 

 layer of snow which protected it from climatological influences. 



3. Quantitative determination of bacteria from soils from different 



localities. This work was a continuation of similar work per- 

 formed in previous years. 



4. Quantitative determination of bacteria from soil from a plot 



covered with snow, in which a gradual horizontal penetration 



Sec. IV. Sig. 2 



