12 president's address. 



slime and fatty matter, is more probable than that the protozoa 

 limit the activities of the bacteria. 



Previous work by Dr. Greig-Smith had shown that the increased 

 fertility of soils, occasioned by the employment of heat or volatile 

 disinfectants, was caused by the heat destroying, more or less, the 

 bacteriotoxins, and by the volatile disinfectants altering the dis- 

 position of the agricere. But there remained the fact that phago- 

 cytic protozoa are in the soil, and that they may have some action, 

 although not to the extent claimed by the Rothamsted investigators. 

 Accordingly, the effect of directly adding protozoa to soil, was 

 tested by noting their effect upon the growth of bacteria. The 

 experimental work showed that the addition of a mixed protozoal 

 fauna or of a pure Amoeba- culture, did not lessen the numbers of 

 bacteria. Instead of doing so, the bacteria always increased. The 

 increase, which always was considerable, was traced to the freely- 

 growing bacteria, which invariably accompanied the protozoa. The 

 use of filtered soil-extracts, upon which Russell and Hutchinson 

 based their idea concerning the activity of the soil-protozoa, did 

 not bear out their contention, as there was so little difference be- 

 twen the action of filtered, as against unfiltered, extracts that it 

 was concluded that the soil-protozoa have no action in limiting the 

 number of bacteria in soils. This has since been supported by the 

 work of Lipman in America. 



Dr. J. M. Petrie, Linnean Macleay Fellow in Biochemistry, con- 

 tributed two papers to last year's Proceedings — "The Chemistry of 

 Doryphora sassafras" and "The Occurrence of Hydrocyanic Acid 

 in Plants (other than Grasses), Part i." — which have appeared in 

 Part ii. of the Proceedings. Part ii. of the latter paper is in pre- 

 paration; and a systematic study of the occurrence of hydro- 

 cyanic acid in grasses, is in progress. About one hundred different 

 grasses have been tested four times during one year, at intervals of 

 three months ; and the presence of hydrocyanic glucosides and their 

 specific enzymes has been demonstrated in about twenty well- 

 known species, but the occurrence is found to vary with the sea- 

 sons. Other investigations are being carried out on the alkaloid 

 Solandrine, on the alkaloids of Duboisia my op oroides, and D. 



