the yield from ioo to 180. and treatment with toluene to 120. These 

 charges are being correlated with a redistribution of the bacterial 

 flora of the soil, together with some direct chemical change brought 

 about by the treatment ; the investigation is not however completed. 



A number of experiments on clover " sickness " have been 

 started, designed with the view of getting some clue to the suscepti- 

 bility of the plant to disease ; and the pots are now awaiting the 

 effect of the winter, during which the killing usually takes place. 



Other investigations of a bacteriological character are intended 

 to deal with more technical points, such as (1) the nature of the 

 competition between the higher plants and the bacteria and fungi for 

 plant food in the soil ; and (2) the growth of plants under sterile 

 conditions with ammonium salts as their sole source of nitrogen ; 

 such work is necessary to provide data for the elucidation of wide 

 practical problems. 



Soil inoculation has occupied a good deal of public attention 

 during the year ; pure cultures of the nodule organisms associated 

 with beans and clover have therefore by request been distributed to 

 members of the various Agricultural Colleges, etc., who wanted to 

 conduct field experiments in that direction ; thirty-eight cultures 

 were thus sent out. 



In connection with the field experiments on the duration of 

 manures and the value of their residues, a series of experiments are 

 being made in the Laboratory on the rate at which the various 

 nitrogenous fertilisers give rise to nitrates in the soil, so as to obtain 

 another measure of their relative activity. This experiment will 

 be continued during several years until the nitrogen applied to the 

 soil has been practically recovered. 



Miss Brenchlev has continued her work on the effect of minute 

 traces of metallic salts on the growth of plants, in order to ascertain 

 metals which are poisonous at high concentrations will stimulate all 

 plants when excessively dilute. Some interesting facts have been 

 observed which are to be verified on a larger scale in the coming 

 year. 



Part of Miss Brenchley's work on the development of the wheat 

 grain has been published ; the chemical side of the work is now 

 being written up. 



The following papers have been published during the year. 

 "Nitrification in Acid Soi/s," by A. D. Hall, N. H.J. Miller, and 

 C. T. Gimingham, Proc. Roy. Soc., B. 80, 196. This paper contains 

 a study of the conditions prevailing on certain of the permanent 

 grass plots to which sulphate and chloride of ammonium has been 

 applied every year, the soil of which is now acid to litmus paper 

 It is shown that the acidity is mainly due to free humic acid, though 

 in the aqueous extract of the soil a little free sulphuric and hydro- 



