110 Proceedings of Indiana Academy of Science. 
BACTERIA IN FROZEN SOIL. 
H. A. Noyes, Purdue University. 
Two soil bacteriologists have published data as showing that the 
number of bacteria in soil increases when the soil is frozen. These 
reported increases in numbers are so contradictory to general belief con- 
cerning bacterial activities at low (about freezing) temperatures that 
not only the experimental data but abstracts of the technic followed are 
given below. 
Figure 1 gives the data presented in Cornell University Agricultural 
Experiment Station Bulletin No. 338. The following is an abstract of 
the technic followed: 
“Samples of soil were usually taken with an auger or by the com- 
bined use of an auger and pick when the ground was frozen. During 
the winter of 1909-1910 a pick alone was used. When an auger was 
employed the proceeds from two or three borings were combined, except 
in winter, when only one hole was made; but when the pick alone was 
used it was impossible to take any such pains in order to obtain a rep- 
resentative sample. * * * The depth of sampling was six to eight 
inches, although in winter 1909-1910 it varied more than during the 
remainder of the period. * * * The soil was carefully mixed, in 
summer by sieving through a sieve as fine as the moisture content would 
allow, in winter by stirring after thawing. Of this soil 0.5 gram was 
added to sufficient sterile water to make a volume of 100 cc. * * * 
The samples taken from any one of these four spots must have all been 
from within a circle of six-inch radius. The media used varied; the 
one most extensively used was soil extract gelatin containing 0.1 per cent 
dextrose. Plates were incubated seven days at 19° to 20° C. for gelatin 
and usually two weeks for agar.’ 
The following statement is taken from the author’s summary of the 
work’: “Quantitative determinations * * * have shown * * * 
an increase in numbers of bacteria in frozen soil.” 
Figure 2 gives the data presented in Research Bulletin No. 4 of the 
Iowa Experiment Station. The following is an abstract of the technic 
followed: 
“The samples were drawn from the plot already described within 
an area of about five feet square. * * * They were taken to a 
1Conn, H. J., in Centrab’t fur Bakt II Abteil. 28 (1910), p. 422. 
