Hoyt: CULTURES OF SPIROGYRA 337 
supply, directly into the culture dishes. The distilled water used 
was from the usual supply of the laboratory, obtained from a local 
druggist. It had been distilled in a copper still and kept in glass. 
All such water used in these experiments was from the same original 
supply and may thus be considered as uniform. The results 
obtained in the study of the physiological properties of various 
waters are given in TABLES II and III. 
Tap water was usually fatal to the plant within a few days, 
although its toxicity varied slightly at different times (II, 1*). 
This water, when distilled with glass boiler and glass condenser, 
Was as toxic as the untreated water (II, 2). The distillate was 
then sampled at different times during the run, by placing culture 
dishes at the outlet of the condenser and allowing them to receive 
the water directly; the alga was introduced into these water 
samples after they had cooled. Samples collected at the beginning 
and end of the run were as toxic as the untreated water (II, 3, 3d). 
About the middle of the run the distillate collected was found to. 
be decidedly less injurious than the untreated tap water (II, 3a). 
Concentration of the tap water to one tenth its original volume by 
boiling (II, 4) and also by allowing evaporation to proceed at a 
temperature much below boiling, till only about a sixth of the 
original volume remained (IJ, 5, 6), produced marked improve- 
ment over the original untreated water, but concentration by 
evaporation to one third of the original volume did not improve 
its quality (II, 7). It will be noted, however, that the untreated 
water of this particular test was more toxic than in the two former 
experiments. In general, concentration seems to have improved 
the quality of the water, probably by driving off some of the 
volatile toxic substances, though it is of course not to be forgotten 
in this connection that the nonvolatile constituents were much 
more concentrated in the treated water than in the original. 
The effect of high temperature without concentration was also 
tested. Heating tap water in the autoclave for 15 minutes, at a 
temperature of 144° C., destroyed all the toxic material, or else 
rendered it nontoxic; in water thus treated Spirogyra filaments 
ee ee a 
* Roman numerals followed by Arabic, in parentheses, refer to table and experi- 
ment, respectively. 
