485 



Subsequent investigation proved that this factor was a class of 

 larger organisms — amoeba or protozoa which under ordinary condi- 

 tions fed on the bacteria and maintained them at a normal number, 

 and that these organisms were completely destroyed by the steriliza- 

 tion process, thus allowing the bacteria to multiply at an extra- 

 ordinary rate. 



These results have since been confirmed by others and by 

 evidence of a different nature, and also by the practice of the 

 agriculturist in ancient days and in other lands than in Europe. 



Science has once more explained facts known long years ago, and 

 will doubtless be able to demonstrate in what way such facts may be 

 utilized again to the best advantage in advancing the ancient art and 

 practice of agriculture. 



Already in fact on a small scale, a method has been adopted, 

 based on these principles, for the sterilization of soils for nursery beds 

 and for intensive cultivation of vegetables and market produce, and 

 it might be of interest and value to give details of this method for the 

 benefit of those who may be interested in the subject. 



The method is described in Vol. VIII, Part 6, of the Journal of 

 Agriculture of Victoria, for June, 1910. 



In this article the writer incidentally mentions the discovery of 

 the action of heat on soils some 25 years ago and the action of car- 

 bon bisulphide, the effect of which was first observed when applied in 

 certain vineyards for the purpose of eradicating phylloxera. 



The various theories to account for these effects are those 

 numerated as follows : — 



(1) . Chemical reaction formed by heat or between antiseptic and 



soils — recently revived by Pickering in England. 



(2) . Physiological theory of Koch — the antiseptics being sup- 



posed to stimulate root activity — since disproved by Rus- 

 sell's and Darbishire's experiments — in which all the 

 antiseptic was evaporated from the soil after treatment. 



(3) . Change of bacterial flora as suggested by Hiltner and Stormc 



(4) . Stoklasa's theory — that the production of too much carbon 



dioxide by bacterial interferes with the plant's respiration 

 does not hold good in the light of Russell's and Hutchin- 

 son's recent investigations. 



(5) . Russell's and Hutchinson's theory— increase of bacteria 



after primary decrease, due to destruction of large organ- 

 isms of protozoal nature. 



