1905] BRIEFER ARTICLES 299 
Five cultures made from different stock material, and always compared 
with controls maintained at the temperature of the conservatory, all agreed 
perfectly in the results. Thus it seems safe to conclude that low tem pera- 
tures act upon the vegetative growth of this alga with the same result as do 
high osmotic pressure and poison cations. No acceleration of zoospore 
formation, a phenomenon often exhibited in poisoned solutions, has been 
observed here. It appears that in low temperature we have another 
method of withholding water from the plant, and that the uniform 
response to such withholding is the production of the palmella form.® 
Fic. 1.—Palmella from filaments like fig. 2 in culture at low temperature. 
Fic. 2.—Normal filaments and germinating zoospores from cold palmella culture 
returned to normal temperature. 
Fic. 3.—Palmella in sea water from normal filaments like fig. 2. 
Il. Sea water.—During my residence at the New York Botanical 
Garden I was able to determine the behavior of this Stigeoclonium in sea 
water. Natural water was collected from the surf at Far Rockaway, L. L, 
and was brought in bottles to the laboratory, where it was used in making 
the cultures. Filaments of this plant placed in undiluted sea water take 
the typical palmella form, as in other solutions of high pressure. Zoospores 
are not produced, nor do those produced previously germinate. Such a 
culture is shown in fig. 3. The water used had a pressure of about 25,000"™ 
of mercury.7_ In sea water diluted to one-tenth and one-hundredth of its 
natural concentration respectively—water redistilled in glass being used 
In the dilution—the response is the same, although the change is not so 
Tapid. In the latter dilution it seems impossible that osmotic pressure 
Is the main stimulating factor, for here is a pressure of only about 250"™ 
° See the remarks on this subject in the paper on chemical stimulation, loc. cit- 
(4), p. 21 et seq. 
7 The calculation was made by the method of the depression of the freezing-point, 
loc. cit. (3), Pp. 37. 
