336 Hoyt: CULTURES OF SPIROGYRA 
medium in a covered Petri dish, produced slight improvement 
in all the 0.1 per cent solutions from ordinary distilled water. 
A good growth was obtained on similar agar plates prepared 
from 0.5 per cent solutions (in ordinary distilled water) according 
to the formula of Sachs, of Molisch, and of Crone.* 
Since the solutions here employed were all prepared from water 
and salts, it will be expedient to present the following considera- 
tions under the two headings: (II) Water and (III) Salts. 
II. WATER 
Many authors have found that tap water and distilled water 
are toxic to organisms, an excellent review of the literature of 
this subject being given by Livingston (12). Most workers have 
attributed the toxic effects of ordinary distilled water to small 
amounts of various metals—especially copper—taken by the water 
from the still and from the supply pipes. Lyon (19) and Bullot 
(6), however, found that water distilled in glass was markedly 
toxic, thus indicating that part of the poisonous action may be 
due to the presence of volatile substances. Lyon attributed this 
effect to small quantities of ammonia in the water. Similarly 
Livingston (12) showed that redistillation from glass to glass, 
while improving the quality of his ordinary distilled water, did 
not render it harmless. He obtained evidence indicating that 
part of the toxic bodies present in ordinary distilled water thus 
redistilled are volatile and reappear in the distillate, while part 
are nonvolatile and remain in the undistilled residue. The same 
writer prepared nontoxic water by shaking ordinary distilled 
water with highly absorbent solids, especially with purified lamp 
black, and then filtering out the solids. He concluded that the 
solids had absorbed, or at least removed from solution, both the 
volatile and the nonvolatile toxic substances. 
In the present investigation both tap water and ordinary dis- 
tilled water were found to be markedly toxic to Spirogyra, and 
were subjected to various treatments in an effort to obtain some 
evidence concerning the nature of the poisonous substances in- 
volved. The tap water was drawn from the faucet of the laboratory 
* Knop’s solution was so acid that 1 per cent agar would not harden ina 0.5 per 
cent concentration of the medium. 
