Tue INFLUENCE OF Low TEMPERATURE ON Sort BAcTERIA 1069 
If there was active growth and reproduction of the ammonifying and 
other types of organisms in the soil, one would expect a protoplasmic 
activity that would be indicated quantitatively or qualitatively by the 
formation of ammonia and similar products. As no change was noticeable 
in the frozen soil, even when large amounts of nitrogenous materials were 
added, it would seem as if bacterial activities had ceased. 
If the bacterial fiora of the soil can withstand the low temperature 
of liquid air for several hours, it seems probable that the mild temperatures 
to which our soils are subjected during the winter would have little or no 
effect in changing the bacterial flora therein, and it will require more 
eareful work than has yet been done on the bacterial activities in frozen 
soils to prove that such a change does take place. 
The results obtained by investigators in the field of soil colloids seem 
to indicate a physical change in the soil due to freezing. It is probably 
this physical change in the soil and its colloids that influences the bacterial 
activities, rather than a change in the bacterial flora of the soil. 
There is a possibility that pressure may play some part in cell division, 
for the soil is subjected to considerable pressure during the formation 
of ice from the soil solution. Kny (1896) noted that pressure actually 
induced cell division in the pith of Impatiens, and that very pronounced 
pressure will cause the periclinal divisions of the cambium to cease and 
anticlinal ones to appear. In many cases he found that pressure induced 
he formation of cell walls at right angles to its line of action. The close 
correlation between the high moisture content and the large number 
of bacteria occurring in the frozen soil seems to favor this theory, for 
the greater the moisture content, the greater would be the pressure. The 
fact that small quantities of soil placed loosely in test tubes and frozen 
showed the same increase, would, however, seem to indicate that the 
increase was not due to pressure. 
The wide variations found by many careful investigators in their 
studies of the influence of low temperatures on bacteria, may be accounted 
for by the difference in the concentration of the media in which the bac- 
teria were grown. The fact that 98 per cent of the organisms growing 
in a very rich nutrient solution survived the low temperature, would 
seem to support the theory that the higher the concentration of the 
medium surrounding the cell, the higher will be the concentration of the 
