Carbon- Assimilation of Marine Algae. 673 
Similar experiments with distilled water gave results slightly 
more favourable than those in Experiment III. In all cases 
in Experiment V, the amount of starch obtained was less than 
in the control in sea water alone, although after five days in 
1 per cent., it was nearly the same. I never obtained a ‘ large * 
amount of starch, but on the other hand the Alga continued 
in good condition for some time, in marked contrast to those 
in KN 0 3 solutions. I concluded that, so far as these experi- 
ments went, sodium nitrate was not able to take the place 
of sodium chloride in regard to C 0 2 -assimilation, and that 
the presence of sodium nitrate in sea water somewhat inhibited 
the power of C 0 2 -assimilation, but not in such a marked 
degree as in the case of potassium nitrate. 
(C) Magnesium Nitrate. 
This is the nitrate which occurs in very small proportions 
in sea water: 1 gram KN 0 3 is equivalent to 1*465 grams 
Mg (N 0 3 ) 2 . 
Experiment VI. June 7, 1900. Sea water + Mg (N 0 3 ) 2 . 
Date. 
Days. 
Equivalent 
toi% KNO. A . 
Equivalent 
too- 5% KNO a . 
Control sea-water 
alone. 
June 12 
5 
little 
little 
moderate 
June 14 
7 
moderate 
large 
maximum 
Experiments in which magnesium nitrate was added to 
distilled water gave results similar to those with sodium 
nitrate. I was not able to make as many experiments with 
this salt as I could have wished, but the results with sea water 
were, on the whole, very similar to those with NaN 0 3 , 
perhaps a little more favourable, but never quite equal to 
the control. 
(D) Ammonium Nitrate. 
With this salt experiments were only made with sea water : 
1 gram KN 0 3 is equivalent to 0-792 gram NH 4 N 0 3 . In 
experiments with quantities equivalent to 1 per cent, and 
