930 
Journal of Agricultural Research 
Vol. V, No. 20 
live for as long as 13 months on cabbage seeds, but when dried on cover 
slips it is dead at the end of 10 days. Briscoe (1) says that this difference 
is no doubt largely due to the difference in the hygroscopic moisture 
retained by these substances. He found that tubercle bacilli lived only 
8 to 12 days when dried in thin smears on glazed-paper slips. Bacillus 
coli t B . violaceus, and B. prodigiosus , according to his experiments, were 
even more sensitive dried under those conditions. 
As to the relative merits of desiccation in room air and in a desiccator, 
some fairly positive statements have been obtained. Chapin (3, p. 195) 
says that as a rule bacteria live longer when dried in a desiccator than 
when dried in the open air under natural conditions. Ficker (7) showed 
that the rapid drying of organisms in a desiccator over calcium chlorid or 
sulphuric acid was preferable to drying in ordinary room air. Ficker's 
experiment (7), in which the organisms were placed alternately in a 
desiccator and a moist chamber for a couple of hours at a time, resulted 
in the organisms so treated dying much more rapidly than did those 
which were left in the desiccator continuously for the same length of 
time. Lohnis (15) states that frequent changes between drying and 
remoistening are most injurious, but that rapid drying in a space with a 
“rarefied atmosphere” (in a desiccator) is comparatively favorable. 
Unpublished experiments of J. Simon have shown that the repeated 
drying and moistening of the soil is much more detrimental to nodule 
bacteria than keeping the soil constantly dry. Chester (4), in his 
experiments with P. radicicola t found that an important condition for 
the successful preservation of the organism in a dry state was to keep 
the culture sealed from the air and in a dark, cool place. 
The evidence obtainable from the literature in regard to the length of 
time an organism may live in air-dry soil and the factors responsible 
for its longevity are neither definite nor complete. Lipman (14, pp. 228 
and 230) says that— 
Under air-dry conditions each soil grain is surrounded by a very thin film of moisture 
designated as hygroscopic water . . . According to Hall the film of hygroscopic 
moisture is about 0.75 11 (0.00003 h 1 -) thick . . . Nevertheless, it will be seen that 
the moisture, even in air-dry material, is deep enough to allow the bacteria a reason¬ 
able amount of protection. This will account for the survival of non-spore-bearing 
bacteria in dry soil for a long time. Indeed, instances are on record of the isolation of 
Azotobacter and Nitrosomonas from soils that had been kept in the laboratory for 
several years. 
Lohnis (15, p. 67) says that— 
vegetative cells can better endure drying when they are in soil. With spores also this 
is true. The resistance of spores dried in earth is usually found to be higher than that 
of spores dried on cotton, silk, glass, etc. 
Duggar and Prucha (6) found that after the rapid drying out of soil 
cultures there remained a large number of living organisms whose vitality 
