1918] BROW N—SPIROGY RA 271 
protoplasts of two of the three cells concerned from fusing. This 
appears to be a common result, and the large proportion of failures 
has been interpreted as proving the abnormality of the method. 
Another illustration included in the paper cited represents a 
condition in S. maxima similar to the one described in this note 
in fig. 2 for S. nitida, excepting the parthenogenetically formed 
spores. The great profusion of conjugation branches exhibited occa- 
sionally by Spirogyra filaments, accompanied by the tendency to 
form abnormal connections, has been regarded as a response to 
environmental conditions exceptionally unfavorable for vegetative 
growth. In this region such external factors as the volume, 
an rCE 
Fic. 3 
temperature, and salt content of water are extremely variable. 
The fluctuation in water volume may be such that in a few days 
a large, rapidly flowing stream is changed to a trickling brook, then 
to a series of stagnant pools, then later to a “dry river” carrying 
its entire flow beneath the surface of the bed. In the winter 
snow water reaches the foothill and mesa country in a cold condi- 
tion after showers in the mountains. Floods of this cold fresh 
water must have a decided influence on the algal vegetation of 
pools by lowering the temperature and salt concentration, increas- 
ing aeration, and thus making the vegetative conditions more 
favorable. Subsequent evaporation and the “run-off” from local 
showers increase the salt content to a maximum and again subject 
algae to unfavorable vegetative conditions, thus bringing on great 
reproductive activity. The Spirogyra figured in this note was 
collected in a pool which had gone through a similar cycle of 
changing conditions. 
University oF ARIZONA 
Tucson, Ariz. 
