554 



FETCH : 



This experiment was repeated with the same sugar cane 

 extract, diluted to contain half the previous percentage of 

 sugar, Avith the following results : — 



Temperatiire, 75 -5-79 -5° F. 



The dry weight of Thielaviopsis in the control culture on 

 December 4 was 0-044 grams; that in the 0*1 per cent, 

 tannic acid culture was 0*025 grams. 0-3 per cent, of tannic 

 acid is the limiting percentage in both cases, i.e., the difference 

 in the percentage of food in the solution does not alter the 

 percentage of tannic acid required to inhibit growth. This is 

 in accordance with the known behaviour of other chemicals 

 on different fungi. It will be noted from the preliminary 

 experiment that the spores are not killed by tannic acid, even 

 if the percentage employed is more than three times that 

 required to prevent the growth of the fungus. 



It was thought that the marked influence of a small 

 percentage of tannic acid upon the growtli of the fungus might 

 serve to explain why the disease does not attack the bud of 

 the coconut, but subsequent analyses have shown that there 

 is no tannic acid in coconut tissues. 



Gallic Acid. 

 (This contained traces of Tannic Acid.) 



Observation. 

 December 12. 



Observation. 

 Deceraber 14. 



December 10. 

 Percentage. 



0-n 



0-2 1 



0'3 J> Growth beginning in all Excellent growth \n all 



0-4 I 

 0-5J 

 Control 



