Studies on Fungicides — III 



03 



holding distilled water only. In this manner three experiments were 

 performed in duplicate. The germination results are given in table 13. 



TABLE 13. Percentage Germination of Sclerotinia Americana Conidia in Water 

 in Contact with Dialyzing Sacs Containing Bordeaux Mixture 



These experiments were further elaborated. An effort was made to 

 determine the effect of dialyzing sacs of varying permeability. Sacs 

 were; prepared in three degrees of permeability — 20-80-2.5, 30-70-2.5, 

 and 40-00-2.5 — and the experiments were run in triplicate with each 

 type. To obviate any complications due to the presence of excess lime, 

 4-4-50 bordeaux was prepared and then centrifuged. The centrifuging 

 made possible the separation of the clear limewater and lime particles 

 from the jelly-like bordeaux membranes. Water was added to the bor- 

 deaux to bring it back to the original strength. The mixture was chem- 1 

 ically tested for free copper, and none was found. The mixture was then 

 placed in the collodion sacs, and these were tied and were sealed with 

 agar. The sacs were placed in pairs in petri dishes containing distilled 

 water, and allowed to stand for two days. The water was then pipetted 

 off and germination tests were made in it. These results are shown in 

 the first column of percentages in table 14. A spore suspension of Sclero- 

 tinia americana was then added to the water surrounding the collodion 

 sacs in the petri dishes. The germination was observed after two days, 

 and is recorded in the second percentage column of table 14. In order 

 to demonstrate whether any free copper was left in solution — that is, 

 whether more copper had been dissolved than was taken up by the 

 spores — the liquid surrounding the sacs was filtered and germination 

 tests were made in the filtrate. These results are given in the third per- 

 centage column of table 14. Finally, to find whether the collodion sacs 

 had leaked, the sacs were carefully rinsed in distilled water, placed in 

 fresh distilled water, and allowed to stand for five days. r l "he water was 

 then pipetted off and germination tests were made in it. The results ol 

 this final test are recorded in the last, column of table II. 



