178 MISSOURI BOTANICAL GARDEN. 
oxygen was deficient in reservoirs where the latter organ- 
isms predominated. 
They found that in general the amount of COz2 varied 
inversely with the amount of oxygen present. When the 
water became thoroughly mixed, through the action of the 
wind, there resulted, as a consequence, an even distribution 
of both the O2 and the COz throughout the vertical. When 
the amount of COz was recorded as zero the water reacted 
alkaline to phenolphthalein, indicating normal carbonates. 
When the amount of CO was recorded as minus it indicated 
the amount of COz2 abstracted from the bicarbonates dis- 
solved in the water. This power to abstract carbonic acid 
from the bicarbonates has been noticed, they say, by several 
observers, but no special attention has been called to the 
phenomenon. The exhaustion of oxygen from the water 
they attribute to the decay of the blue-green alge; for, with 
the return of oxygen after the decay of the blue-green alge, 
the grass-green alge increased in amount and were believed 
to be the source of the excess of oxygen, which reached 149% 
of saturation. Stirring up the water and exposing different 
parts to the wind tends to reduce the amount of COz in 
the water and at the same time increase the amount of 
oxygen in the water by aération. If the circulation is a 
gentle one it may increase the amount of COz2 by distribut- 
ing throughout the mass that which is found at the bottom; 
but if the circulation is violent it may tend to decrease the 
COsz by losses into the atmosphere at the surface. 
Morren (’41), who made an extensive study of ‘‘water- 
bloom,” and especially that form known as red or bloody 
water, claims that the amount of oxygen and CQ2 varies 
reciprocally with the amount and kind of organisms found 
in the water; increasing during the day on account of the 
rapid photosynthesis of the green or reddish organisms, and 
diminishing in the night (the amount of oxygen) on 
account of the rapid respiration of the same organisms. 
Moreover, he claims that the color of these organisms is 
so much dependent on the oxygen content of the water 
that he can control the color by varying the supply of 
