Studies on Fungicides — III 



71 



TABLE 19. Percentage Germination of Sclerotinia Americana Conidia in Solu- 

 tions of Copper Sulfate and Suspensions of an " Insoluble " Copper Dust 



A similar experiment was performed with copper sulfate and insoluble 

 copper phenyl acetylide (CuC 8 H 5 ). 3 Spores of Macrosporium sarcinae- 

 forme were used. The results appear in table 20. 



TABLE 20. Percentage Germination of Macrosporium sarcinaeforme Spores in 

 Solutions of Copper Sulfate anl- Suspensions of Insoluble Copper Phenyl 

 Acetylide 



Discussion. Following the reasoning advanced above, the results shown 

 in table 19 seem to point clearly to a solvent action on the part of the 

 fungus spores. However, it is possible also that any cumulative action 

 may be masked by that of the spore-excretion solvent. 



In table 20, spore-solvent action appears to be much less marked. This 

 perhaps may not be unexpected, since copper phenyl acetylide is not 

 ordinarily used as a copper protectant and hence need not necessarily 

 be expected to possess protectant properties. On the other hand, there 

 is a lack of evidence in support of the cumulative-action hypothesis. 



In conclusion it may be stated that these preliminary experiments fail 

 to give any very substantial evidence on the cumulative-action hypothesis. 



3 The copper phenyl acetylide was kindly furnished by Professor J. It. Johnson, of the Department of 

 Chemistry, Cornell University. 



