of Carbon Dioxide in Ulva latissima , L, 47 
Experiment IV. April 19, 1900. Starch-free Ulva in 
distilled water. 
Date. 
Days. 
Amount of Starch. 
Apr. 20 
1 
a trace 
Apr. 21 
2 
a little 
Apr. 22 
3 
Apr. 23 
4 
Apr. 24 
5 
Apr. 25 
' 6 
»* 
Apr. 26 
7 
” 
Usually after a week or even less in distilled water the 
Alga became unhealthy ; the solution would become cloudy 
with Bacteria and the Alga fragmentate. I cannot but con- 
clude, however, that this result was not due directly to the 
distilled water. Naegeli and others have found that distilled 
water has a poisonous or an injurious, if not fatal, action on 
plants. Naegeli 1 attributed this to the presence of a trace 
of copper, and found that one part of copper in a thousand 
million parts of water was fatal to a Spirogyra filament. On 
the other hand, Klebs 2 , Oltmanns 3 , Molisch 4 , and others, 
have made use of distilled water in connexion with the 
cultivation of Algae without any disastrous results. The 
distilled water used in this work was the ordinary distilled 
water as supplied to the laboratory and not re-distilled, and 
was made use of in all my experiments wherever sea water 
or tap water were not employed. The fact that, whenever 
a sufficient amount of nutrient salts was added to such water, 
there was always, with the exception of a very small margin 
of failures, a greater or less amount of carbon-assimilation — 
the amount of starch often reaching the maximum — seemed 
to show conclusively that the distilled water in itself had no 
injurious effect. In Experiments IX-X (p. 61) and XII-XIII 
(p. 64), the cultures were extended for fully a month. 
1 Naegeli; vide Pfeffer (’00), p. 221. 2 Klebs (’96). 
3 Oltmanns (’92). 4 Molisch ('951 
