EXI'KIJI.MKN'L' STATION KKl'OlJT. 539 



that is, three ounces of tlie carbonate of copper to oni' quart of am- 

 iiiouia. By this the spores were killed, as also hy the half, fifth and 

 twentieth strength. An extreme dilution was tiicn substituted, 

 namely, a one per cent, strcnsith of the funuieide, as us<.'d for s])ray- 

 ing grapes, etc. — that is, one part of the ordinary vineyard strength 

 was added to ninety-nine of pure water, which gave a liquid that 

 contained so little copper as to require a most delicate chemical test 

 to detect its presence. In such a solution the spores would not germi- 

 nate, but after several days, when the spores were washed five times 

 and placed in pure water, they grew slowly. In order to carry the 

 tests a step farther, slides with pit cells were arranged, with pun? 

 water in each, but into alternate ones a small bit of polished copper 

 foil was dropped, the piece being in area equal to that of the lead at 

 the end of a Faber pencil. That the presence of this minute amount 

 of metallic copper should prevent the germination of the spores was 

 surprising, and only after many trials was the fact accepted. In only 

 one case in a score or more was any spores with the copper found with 

 germ-tubes, and in this they had probably formed before the sowing 

 was made. In no instance was there any failure of the spores to grgw 

 in the check-cells witii pure water only. That there might be no 

 chance of any oxide of copper or other soluble compound Ix-ing pres- 

 ent, the foil was thoroughly scoured and rubbed to a bright polish. 

 After the bit of copper was removed and the water changed, the spores 

 would sometimes germinate, the degree of activity depending some- 

 wiiat upon the length of time they had been held in check. 



"If now, in place of pure water in a fresh preparation, a percentage 

 of cherry juice is added to the slide-well, the spores grow, the rate 

 depending upon the amount of stimulating fiuid added. A point 

 could doubtless be reached at which the action of the nourishing flui<I 

 would just equal that of the copper, and the spore would remain 

 alive and inactive indefinitely. 



•"While at first sight there does not seem to be any practical bearing- 

 for these results, upon a further consideration it may teach the trutlt 

 that fungicides, as at present emjjloyed, are far stronger than they 

 may need to be. If a bit of metallic copper in pure water will hold 

 its own weight, or many times that of spores inactive, it seems likely 

 that the time has come to try a weaker solution of copper. 



"Since the above was written opportunity has offered to test the 

 spores of a species of Fusarium and tliose of Cercospora Apii Fr., the 



3i 



