NOTES AND ABSTRACTS. 
515 
may receive protection from the solution in which it is suspended, before being 
subjected to desiccation in sand. Cultures of Pseudomonas radicicola were 
used and the following solutions were employed : 
1. Physiological salt solution ; 
2. „ „ 4 o-i per cent, of agar. 
3. „ „ + o-i „ „ gelatine. 
4. + 0,1 »» >> albumin, 
5. ,, + o-i „ ,, gum arabic. 
6. + o-i „ soluble starch. 
Suspension of the bacterial growth from agar slopes was made in 250 cc. 
of each of the above solutions ; and sterile quartz sand was inoculated with 
5 cc, of the solutions. At intervals, the number of organisms in one gram of sand 
was determined by plate cultures. Other experiments were made using clay, 
clay loam, sandy loam, in place of sand. 
The general conclusions were : — ■ 
1. Bacteria, at least those tested, resist desiccation longer in a rich clay 
loam than in sand under the conditions of these experiments. 
2. If bacteria are suspended in a solution extracted from a rich clay loam, 
before being subjected to desiccation in sand, they live longer than if subjected 
to desiccation after suspension in physiological salt solution. 
3. The survival of non -spore-bearing bacteria in air-dry soil is due, in part, 
to the retention by the soil of moisture in the hygroscopic form. This, however, 
is not the only factor, for the longevity of bacteria in a soil is not directly pro- 
portional to its grain size and hygroscopic moisture. — A. B. 
Soil Protozoa, Separation of. By N. Kopeloff, H. C. Lint, and D. A. 
Coleman (Jour. Agr. Res. v. No. 3, Oct. 1915. PP- 1 37-14°) • — Gives a brief 
account of a method of filtration whereby flagellates, small ciliates (12 to 20 /x), 
and large ciliates (25 to 60 /x) were readily separated from an eight-day culture 
on a soil medium. 
It is shown that the three types of protozoa can easily pass through the 
pores of a filter, but can be arrested if various thicknesses of filter paper are 
used. With one thickness no large ciliates passed through, while with four 
thicknesses only flagellates were able to pass through. With five thicknesses 
no protozoa, whether flagellate or ciliate, were found in the nitrate. It is suggested 
that in this way it becomes possible to use mass cultures of flagellates, small 
ciliates, or large ciliates, as may be required in experimental work on soil protozoa. 
A. B. 
Soil, Spore-forming Bacteria in the ; their Significance, if any. By H. Joel 
Conn (U.S.A. Exp. Stn., New York, Tech. Bull. 51, March 1916, pp. 1-9). — As a 
result of his experiments, the author doubts the common assumption that spore- 
bearing bacteria (e.g. B. mycoides, B. cereus, B. megatherium) are important 
ammonifiers in the soil. They raise the question as to what possible soil conditions 
favour their growth and multiplication. 
The number of spore-bearing bacteria is relatively constant, and is about 
the same in all the soils studied. Three of the commoner spore-bearing bacteria 
were selected for comparison, because their colonies on gelatine plates are easily 
distinguishable. The total number of these three organisms (B. mycoides, B. 
cereus, B. megatherium) proved to be between 400,000 and 1,500,000 per gram 
in the soils studied. They always comprised less than 10 per cent., and usually 
less than 5 per cent., of all the colonies developing on gelatine. 
When soil infusion was heated, before plating, at a temperature (75°-85°C.) 
high enough to kill the vegetative forms of bacteria, nearly if not quite as many 
colonies of these spore-forming bacteria developed as when it was plated un- 
heated. In about one-third of the cases, indeed, their numbers were actually 
slightly higher on the plates made after heating. This suggests that these bacteria 
occur in normal soil as spores rather than in a vegetative state. 
No increase in the total number of these organisms, nor increase in the 
number of their spores, could be detected in a pot of soil to which fresh manure 
had been added. — A. B. 
Soil, Studies of a Scottish Drift. Part I. By James Hendrick and 
William G. Ogg (Jour. Agr. Sci. vol. vii. pt. 4, pp. 458-469). — Part I. of this 
investigation deals with the composition of the soil and of the mineral particles 
which compose it. The soil is that of the farm of Craibstone, which is the experi- 
mental station of the North of Scotland College, and is situated six miles from 
Aberdeen. The samples were first mechanically analysed under the six standard 
