154 CONTRIBUTIONS TO OUR KNOWLEDGE OF SOIL-FERTILITY, xvi. 



1 have found, in the past, that soils are more toxic in the 

 winter than in the summer-months, and it is to be expected that 

 temperature will have some influence in either the production or 

 the decay of the toxin. The influence of temperature was tested 



in the following. 



The experiment was rather disappointing, as there was little 

 evidence of toxin-formation at the lower or the higher tempera- 

 ture. In four days at 15'5° it is shown by the low extract/water 

 ratio that much of the nutriment has been locked up in the bodies 

 of the bacteria. As the ratio is higher on the eighth day, one 

 would imagine that there had been some dissolution of the cells. 



In an earlier experiment, there had been signs that some 

 formation of toxin had occurred in a solution of gum-arabic 

 infected with Bac. '1\P.2. This led to the employment of an old 

 culture of Rhizobium which had been grown in hay-infusion and 

 dextrose, and which contained a quantity of slime. It was 

 sterilised and infected with Bac. T.P.2. It showed no signs of 

 toxicity on the third day. 



An old culture of Bac. T.P.2 in hay-infusion was sterilised and 

 infected with Bac. T.P.2, but there were no signs of toxicity on 

 the second or fourth day. 



A solution of Gum-Acacia, 0-2%, when infected with Bac. 

 T.B.2, showed no toxicity on the second or fourth day. 



