408 MINNESOTA BOTANICAL STUDIES 



plies has been practiced for more than ten years. The discovery 

 by George T. Moore, in 1901, of the effect of copper sulphate upon 

 Spirogyra in water-cress beds, and the publication by Moore and 

 Kellerman of the Bureau of Plant Industry, U. S. Department of 

 Agriculture, of a couple of bulletins ^ in 1904 and 1905, on the 

 effect of copper sulphate upon bacteria and algae in water supplies, 

 led to quite an extensive use of copper sulphate throughout the 

 country. As early as 1905, the Journal of New England Water 

 Works 2 gives a table, compiled from those who had used the 

 copper sulphate treatment, showing the results of many experi- 

 ments. This table contains definite information on several points, 

 the size of the reservoir treated, the strength of the treatment, the 

 name of one or more organisms causing trouble, and the general 

 effect of the treatment upon the organism or organisms causing the 

 trouble. The report covers some twenty-seven cities, representing 

 more than a dozen different states. Both the strength of the treat- 

 ment and the organism causing trouble varied a good deal in differ- 

 ent places. The strength of the treatment was in most cases some- 

 where between 1 to 8,000,000 and 1 to 1,000,000, and the alga most 

 frequently reported as causing trouble, was Anabaena. The results 

 were almost uniformly favorable — destruction of the troublesome 

 alga and disappearance of all disagreeable taste and odor from the 

 water in a few days. In about one half of the cases cited the algae 

 appeared again the same season, one, two, or three months after the 

 treatment. In several cases where the algae did not occur again dur- 

 ing the same season, the treatment was made rather late in the sea- 

 son, in August, September, October, or even as late as November, 

 and the lateness of the season was doubtless largely responsible for 

 their inability to get a second start. 



Caird,^ one of the early workers with the copper sulphate treat- 

 ment, obtained some interesting results in treatment of reservoirs 

 under normal conditions in 1904 and 1905, and gives in his reports 

 the effect of several treatments of different strength, upon several 

 algae common in the reservoirs treated. 



Lovejoy's'* experiments at Louisville in connection with filter 

 troubles in 1909-10 are especially interesting. He found in 1909, 

 when several organisms were clogging the filters, that by using 14 

 pounds of copper sulphate per million gallons of water, the filter 

 runs were increased from two hours to the normal of twelve or 



