740 TRANSACTIONS OF SECTION M. 
tion from the plant, and its replacement by air at ‘ screen-temperature.’ Tran- 
spiration of water from the plant is negligible at night. 
The usual Egyptian paradox follows, since the wind which cools the grower 
warms the plant. 
2. The Action of Quicklime on the Soil. 
By H. B. Hurcutnson, Ph.D. 
An account of experiments designed to show how far the micro-organisms of 
the soil are affected by applications of caustic lime was given. The addition of 
small quantities of quicklime to field and garden soils stimulates general bacterial 
growth, but large quantities cause an initial depression in the numbers of bacteria 
and the destruction of certain large protozoa, and a cessation of all biological 
processes. 
Conversion of the lime from the caustic form into the carbonate or com- 
bination with soil compounds is followed by a great increase in the numbers of 
bacteria and increased ammonification of soil compounds. 
The length of the period during which bacterial growth is suspended would 
appear to be determined by the quantity of lime applied, the initial reaction of 
the soil, and the amount of organic matter present. 
Pot experiments have been carried out with variously limed soils, and the 
crop results show close agreement with those obtained by bacteriological and 
chemical analyses. 
3. Studies on Nitrogen Assimilation by Free-living Organisms. 
By H. B. Hurcuinson, Ph.D. 
Plots of land, when allowed to run wild for some years, show a considerable 
accumulation of nitrogen in the upper layers of the soil. This has been attributed 
to the utilisation of the plant residues for nitrogen assimilation by such 
organisms as Azotobacter chroococcum. 
Attempts to induce similar changes in field soils have been made at Rotham- 
sted, and the halves of two of the continuous barley plots on Hoos Field have 
received spring or autumn applications of sugar or starch for some years. 
Spring applications of carbohydrates were made in the four years 1906 to 1909, 
and were followed by decreased crop yields. Laboratory experiments showed 
an increase of general saprophytic bacteria and a withdrawal of available 
nitrogenous plant-food from circulation in the soil. It also appeared probable 
that the soil temperature obtaining in spring was too low to allow of a vigorous 
growth of the nitrogen-fixing organisms in the soil. Autumn applications were 
made in 1909 and 1910 and resulted in a decided increase of yield over the control 
ylot. The results are shown in the following table :— 
Hoos Field Barley: Effects of Sugar (or Starch) on the Amount of Produce. 
(Plot 40, Complete Minerals.) 
| | 
| ¥ Sdnan (op Siarcky Total Produce of Barley Relative Yields. 
ee Applied i : Control=100 
Without Sugar With Sugar 
Lb. Lb. 
1906 Spring 2,485 +* — 
1907 T ” 3,578 3,249 91 
1908 - 1,820 1,404 77 
1909 “3 2,563 2,261 80 
1910 Autumn 2,082 2,502 120 
1911 + 1,244 1,915 154 
** Very small crop, not weighed. 
++ Starch applied instead of sugar in 1907. 
