32 S. E. A. McCallan 



ferrocyanide added to copper hydroxide in distilled water, and the whole 

 placed in a dish covered with paraffin, showed no color after a month, 

 whereas a similar mixture in an open dish showed the red color after 

 one day. 



Botrytis spores were placed by Schmidt in distilled water in an open 

 dish and allowed to germinate for 48 hours. A control without spores was 

 exposed for 4 hours. To each there was then added a little copper hydrox- 

 ide, and after 30 minutes a test for soluble copper was made with potassium 

 ferrocyanide. The test was positive and of equal intensity for both. 



In another experiment Schmidt allowed distilled water to stand on cop- 

 per hydroxide for four weeks, and then filtered. Botrytis spores were 

 placed in the filtrate, and also on the precipitate, to which fresh distilled 

 water had been added. These were each divided into two series; to one 

 a little sugar was added, and to the other none. The results after three 

 days were good germination in the precipitate, both with and without 

 sugar, about one-third germination in the filtrate with sugar, and no 

 germination in the filtrate without sugar. From this Schmidt concludes 

 that the four-weeks-old filtrate was more toxic than the precipitate sus- 

 pension in fresh water, and that this difference was due to the time of 

 standing exposed to the atmosphere. 



Schmidt also prepared four sets of tubes, in each of which was placed a 

 suspension of copper hydroxide in distilled water. Trichothecium spores 

 were sown in two of the sets, and the ends of the tubes of one set were 

 sealed with paraffin. One of the two remaining sets was likewise sealed. 

 After standing thus for 48 hours, potassium ferrocyanide was added to all 

 and the color reaction was observed in 5 hours. The two sealed tubes 

 gave a very slight reaction for soluble copper, while the unsealed tubes 

 gave a very decided reaction, thus showing the presence of soluble copper. 

 There was no apparent difference in the tubes with or without spores. 

 This test was repeated with bordeaux mixture and spores of Botrytis and 

 Aspergillus. The results were more marked this time, in that there was 

 no reaction at all in the sealed tubes. 



A similar type of experiment was set up by Schmidt, in which washed 

 copper hydroxide was placed in watch glasses in distilled water. Half 

 the glasses were placed in a desiccator over potassium hydroxide. The 

 other half were left exposed to the air. To half of each of these sets, 

 Botrytis spores were added and allowed to germinate for 48 hours, when 

 potassium ferrocyanide was added to all. After another period of 48 

 hours there was only a very slight positive test for copper in the glasses 

 in the desiccator, but after only 5 hours there was a very positive test in 

 the exposed dishes. Schmidt states that the spores in all the dishes gave 

 about 50 per cent germination. This appears very inconsistent with the 

 fact that he found such marked differences in the amounts of soluble copper 

 in the two sets. 



