EFFECT OF COPPER SULPHATE. 17 



ments of Israel and Klingman a the presence of 60 sq. cm. of copper 

 foil in 300 cc. of water for twenty-four hours produced plasinal cut- 

 ting in S. laxa after one and one-fourth hours, in S. crassa after fifteen 

 minutes, and in S. majuscula after thirty minutes. The work of 

 Rumm 6 shows 1 to 10,000,000 solution still toxic to a few more sus- 

 ceptible cells of S. longata. According to Ono, c weak solutions of the 

 salts of most of the metals encourage the growth of algae and fungi. 

 Mercury and copper, however, at 0.00005 per cent and 0.00001 per 

 cent, respectively, distinctly inhibit growth. This was the case with 

 Stigeoclonium, Chroococcum, and Protococcus. 



In the experiments conducted in this laboratory it has not been pos- 

 sible as yet to include all of the organisms known to pollute water 

 supplies. It is believed, however, that, pending the completion of 

 more extensive work, the data at hand will be of considerable benefit 

 to those who have to deal with contaminated reservoirs. The method 

 of procedure in studying this question was to determine roughly the 

 death points of the forms under consideration, using Van Tieghem cells. 

 Accurate solutions were then made, with distilled water, and 200 cc. 

 of each solution was pipetted into an Erlenmyer flask. The algae, if 

 filamentous forms, were rinsed; if free-swimming, they were concen- 

 trated b}^ the Sedgwick-Raf ter d method from 500 cc. to 5 cc. volume, 

 and this 5 cc. was added to the treated water. The inaccuracy due to 

 the addition of the 5 cc. of untreated water to the 200 cc. of treated 

 water was disregarded. Whenever possible, a test of these concen- 

 trations, determined experimentally, was made under natural conditions 

 by treating the pool from which the species under consideration was 

 taken. If this was impracticable, an additional series was carried 

 through in aquaria of 15 liters capacity, in which were kept goldfish, 

 frogs, minnows, Crustacea, and rotifers. Since in no case was there 

 an appreciable difference in the effect of a concentration upon a par- 

 ticular organism under either natural or artificial conditions, no special 

 record is made of these gross experiments. 



The different species tested may, for convenience, be grouped as (1) 

 those with death points at higher concentrations than 1 part copper 

 sulphate to 1,000,000 parts of water; (2) those with death points between 

 1 to 1,000,000 and 1 to 5,000,000; and (3) those with death points at 

 greater dilutions than 1 to 5,000,000. 



Israel and Klingman, Virchow's Archiv., 147: 293. 



6 Rumm, Beitrage zur Wissenschaftliche Botanik, 1 : 97. 



f Ono, Journ. of College of Sc., Imp. Univ. Tokyo, 13: 141. 



d Whipple, The Microscopy of Drinking Water, New York, 1899, p. 15. 



