16 METHOD OF DESTROYING ALG^E IN WATER SUPPLIES. 



seems that copper sulphate is the substance best adapted to the work 

 in question. This salt has a very high toxicity for algae, and experi- 

 ments with a number of the forms usually found in reservoirs, and 

 the source of much trouble, have shown that inconceivably small 

 amounts of copper are poisonous in a high degree. These experiments 

 demonstrated, however, that all algae and protozoa are not equally sen- 

 sitive. Among the latter Params&dum is killed in three hours by a 1 

 to 1,000,000 solution, while A.?nceba, Diffiugia, and Spi/rost&mum die 

 within two hours. Crustacea are more resistant, some Cypris and 

 Daphnia especially requiring as much as 1 part copper sulphate to 

 10,000 of water to kill them. Mosquito larvae die at a concentration 

 varying from 10,000 to 200,000. 



Quoting the results of other experimenters, Devaux a found that 

 both phaenogams and cryptogams were poisoned by solutions of copper 

 diluted to the ten-millionth part or less; Coupin & that 1 part copper 

 sulphate to 700,000,000 of water was sufficient to affect the growth of 

 seedlings when applied to their roots and that this is the most inju- 

 rious of the heavy metal salts tested by him; Deherain and De Moussy c 

 that the development of the roots of seedlings was arrested in distilled 

 water containing the slightest trace of copper, and they conclude from 

 this that higher plants during germination, as well as fungi and algy?, 

 are extremely sensitive to copper; Bain's experiments d indicated that 

 1 part of metallic copper to 25,000,000 of water was fatal to apple seed- 

 lings in one day; on the other hand, according to Raulin/ copper chlo- 

 ride does not injure Sterigmatocystis until a concentration of 1 to 240 is 

 reached, although silver nitrate is toxic at 1 to 1,600,000. 



In dealing with algae, the toxic concentration varies greatly for dif- 

 ferent genera, even for different species in the same genus. Nageli ; 

 demonstrated the extreme sensitiveness of Splrogyra nitida and S. 

 diibia to the presence of copper coins in the water. Oscillatoria, 

 Cladophora, (Edog&nium, and the diatoms succumb in six hours 

 to a copper sulphate solution of 1 to 20,000, and in two days to 1 to 

 50,000, according to Bokorny.* 7 Galeotti A finds that a concentration 

 between 1 to 6,300,000 and 1 to 12,600,000 is sufficient to kill Spiro- 

 gyra nitida in two days, and that the so-called colloidal solutions at 1 

 to 6,300,000 are fatal in the same length of time; while in the experi- 



Devaux, Compt. Rend., 132: 717. 

 &Coupin, Compt, Rend., 132: 645. 

 ^'Deherain and De Moussy, Compt. Rend., 132: 523. 

 ^Bain, Bull. Agr. Exp. Sta. Tenn., April, 1902. 

 "Raulin, Ann. des So. Nat. Bot., 5 C Ser., II: 93. 



/Nageli, Ueber oligodynamische Erscheinungen in lebenden Zellen. Neue 

 Denkschr. d. schweizerischen Gesellsch. fiir die gesammten Naturwiss., 33: 51. 

 r/Bokorny, Arch. f. d. ges. Phys. d. Mensch. u. Thiere, 64: 262. 

 ''Galeotti, Biol. Centralbl., 21: 321. 



