Studies on Fungicides — III 



61 



TABLE 12. Solvent Action on Copper-Lime Dust of Filtrates from Suspensions 

 of Germinating Spores: Percentage Germination of Sclerotinia Americana 

 Conidia in the Filtrates 



Discussion. The results of these repeated experiments with bordeaux 

 mixture and copper-lime dust lead to but one conclusion, namely, that 

 excretions from germinating spores are active in bringing the copper into 

 solution from the insoluble fungicide. 



Although the amount of copper rendered soluble in these experiments 

 was not sufficient to entirely inhibit the germination of the spores, it 

 must be borne in mind that here both the solvent principle and the soluble 

 copper were doubtless greatly diluted. 'In nature the reaction of single 

 isolated spores possibly differs, in that there is perhaps a greater concen- 

 tration of soluble copper about the spore. 



In these experiments the " spore filtrate," or filtrate from the solution 

 in which the spores had germinated, was not found to be toxic to the 

 spores even after standing for two days. This, therefore, cannot be a 

 factor in the toxicity of the solutions. Likewise, as was previously shown, 

 the action of atmospheric agencies on these copper protectants while in 

 contact with distilled water was not sufficient to liberate any appreciable 

 quantity of soluble copper. 



From these experiments it cannot be determined at what period of 

 germination, if any, the production of the excreted solvents by the spore 

 is most abundant. It is perhaps possible that a spore, even in its normal 

 life processes before germination has begun, may excrete dissolving 

 materials. 



