1906] OSTERHOUT—BALANCED SOLUTIONS 129 
Ptilota filicina, Pterosiphonia bipinnata, Iridaea laminarioides, 
Sarcophyllis pygmea, Nitophyllum multilobum, Porphyra naiadum, 
Porphyra perforata, Gelidium sp., Gymnogongrus linearis, Gigartina 
mammillosa.? 
If plants of either group be placed in a solution of pure sodium 
chlorid (isotonic with sea water), they die in a short time. This 
might be attributed to the lack of certain salts which are necessary 
for their metabolism, rather than to the toxicity of the sodium chlorid. 
In the case of the plants of Group 1 there can be no doubt on this 
point, for these plants live a long time in distilled water. If we add 
pure sodium chlorid to the distilled water it kills them in a very 
short time. An inspection of the tables will show that. these plants 
in their behavior toward sodium chlorid and other salts, closely 
agree with those of Group 2, which can live but a short time in dis- 
tilled water. Sodium chlorid is certainly toxic to the first group, 
and there can be little doubt that it is so to the second group as 
well. 
The plants of the first group were found in a ditch in a salt marsh 
through which the tide ebbs and flows; there is always a foot or 
So of water even at low tide. The salt content of the water fluctuates 
around a mean of approximately 2.3 per cent. 
The plants of the second group were collected at the entrance to 
San Francisco Bay, where the salt content of the water fluctuates 
about a mean which is probably not far from 2.7 per cent. The 
only exceptions are Enteromorpha intestinalis and Ectocarpus con- 
jervoides, which came from wharves in the bay, where the mean salt 
content is about 2.3 per cent. 
All the plants used in the experiments were transferred from the 
sea water directly to distilled water. After rinsing in this they were 
Placed in glass dishes, each containing 2c0°° of the solution to be 
tested. The dishes were then covered with glass plates to exclude 
dust and check evaporation. Only a small amount of material was 
Placed in each dish. The temperature during the experiments did 
not vary far from 18° C. 
Artificial sea water was prepared} according to VAN ’t Horr’s 
? The determinations were kindly made by Professor SETCHELL. 
’ The water used was distilled in glass only and the first part of the distillate 
rejected. The purity of each salt was carefully tested before using. 
