of Carbon Dioxide in Ulva latissima , L, 63 
The conclusion with regard to these chlorides (provisional 
in the case of Mg Cl 2 ) was that the presence of either salt 
by itself in any percentage tried was not favourable to the 
maximum, or even to a moderate degree of carbon-assimilation. 
In the case of K Cl the amount of starch was even smaller in 
many cases than that which would have been formed in dis- 
tilled water alone. 
(C) NaBr. 
A few experiments were made with sodium bromide to 
see whether this salt could take the place of the similar salt 
NaCl. The concentrations used were 1, 2, and 2-5 per cent. 
NaBr. Six experiments with these percentages all gave very 
similar results. Some starch was formed in all cases, but a 
4 little ’ was the largest amount obtained after repeated testings 
for a week or more. Bromides are known to be non-injurious 
if sufficiently dilute, but as far as these experiments go NaBr 
did not seem able to take the place of Na Cl in regard to 
carbon-assimilation. 
Section VII. Sulphates. 
The two sulphates which occur in sea water are MgS 0 4 
(0-2 per cent.), and Ca S 0 4 (o-i per cent.). Calcium, and pro- 
bably also magnesium, are essential in the case of the higher 
Algae, as has been shown by the recent researches of Molisch l , 
Klebs 2 , Benecke 3 , and Loew 4 . 
Experiments were made with an artificial sea water, in 
which all the principal salts were present in the usual pro- 
portions, with the exception of magnesium sulphate in the 
one case, and calcium sulphate in the other. Distilled water 
was used as before and the Ulva freed as far as possible from 
sea water beforehand. In neither case did the absence of 
these salts seem to affect the carbon-assimilation. 
1 Molisch (’95). 
3 Benecke (’98). 
2 Klebs (’96). 
4 Loew (’98). 
