1046 A. F. Vass 
Bartram (1916) exposed several of the disease-producing bacteria to 
- winter temperatures for several months. Of the six cultures exposed, 
only two survived. 
SOIL FLORA 
Among the early workers who studied the influence of temperature 
on the bacterial flora of the soil may be mentioned Remy (1902), who 
studied the seasonal variations. His quantitative study showed no great 
variation in the different seasons. No samples were taken during the > 
winter. 
A correlation between the number of bacteria in the soil and the mois- 
ture content was noted by Hiltner and Stormer (1903). Their results 
indicated also that there was a decrease in the total number of bacteria 
as the temperature of the soil was lowered. They noted, however, that 
certain of the frozen samples gave rather high results. Fabricius and 
Von Feilitzen (1905) found the same correlation to exist between tempera- 
ture and the bacteria count. Their tests were made during the growing 
season. 
Engberding (1909) concluded, from his studies of bacterial activity 
in fallow and cropped, and manured and unmanured, plots, that the 
moisture content was more important than the temperature. Most of 
his samples were taken during the period of plant growth. Of the two 
frozen samples studied, the counts were not so high as in some of the 
unfrozen samples, but they were sufficiently high to show that there are 
large numbers of bacteria in frozen soil. 
Conn (1910) made a careful study of the bacterial flora. thruout the 
year. He concludes from his results that quantitative determinations 
by means of the gelatin-plate method show that bacteria may be present 
in the soil in large numbers during the winter, and that there seems to 
be a rapid multiplication of bacteria in frozen soil. He noted that the 
number of bacteria increased and decreased nearly parallel with the 
moisture content of the soil in the frozen samples, but during the winter 
there was a striking exception to this. In a continuation of the above 
work (Conn, 1912) his earlier findings were confirmed. The same marked 
increase in number of bacteria in frozen soil, and decrease in thawed soil, 
was noted. The increase during the winter was thought to be due to the 
actual multiplication of the bacteria rather than to a mere rise of the 
organisms from lower depths brought about by mechanical forces alone. 
