56 



S. E. A. McCallan 



to each jar. The jars were then connected to a water suction pump in 

 such a manner that fresh air was continually and vigorously drawn through 

 the water, bathing the fungicide-coated surfaces. The water level was 

 kept constant by daily additions of fresh distilled water. A second set 

 was maintained, in which the fungicides were merely placed in open petri 

 dishes and water was added as in the previous method. 



In the first and second tests the air was allowed to bubble through for 

 9 days. In the third test this period was 8 days. At the end of these 

 periods all the suspensions — those in the jars through which air had boon 

 passed, and those standing in the open petri dishes — were filtered through 

 ordinary laboratory filter paper. Chemical tests with potassium ferro- 

 cyanide and potassium mercuric thiocyanate at this point failed to demon- 

 strate the presence of soluble copper in any of the nitrates. At the out- 

 set of the experiments, similar tests of the filtrates from the fungicides 

 had failed to show any soluble copper. 



Germination tests were made with the filtrates. Although the filtrates 

 failed to react to the chemical tests, it was thought that sufficient copper 

 might be present to warrant a dilution. Thus, to attempt a differentia- 

 tion of the filtrates, they were diluted with distilled water to one-half, 

 one-third, and one-quarter strengths. These concentrations — full, one- 

 half, one-third, and one-quarter strengths — are respectively designated 

 as filtrates 1, 2, 3, and 4. The results of the germination tests are shown 

 in table 9. 



TABLE 9. Percentage Germination of Spores in Filtrates from Distilled Water 

 on Copper Protectants Exposed to Various Treatments 



