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RELATION OF ALGAE TO DISSOLVED GASES. 173 
afford protection from rough waves or currents. Where 
currents were most constant, if not too violent, bringing 
a supply of COz and removing the excreted oxygen, an 
important factor in the growth of aquatic plants, there the 
largest growth was found, both as to size of individuals and 
total bulk of plant growth. . 
Lacking facilities at the time for measuring the gas 
content of the water, that point was necessarily left 
unsettled, and the problem, so far as that region is con- 
cerned, was dropped indefinitely. Some two years later, 
this phase of the problem was taken up at the Missouri 
Botanical Garden. Although the conditions are quite dif- 
ferent in small bodies of fresh water from those just cited 
in larger bodies of salt water, yet Birge and Juday (’11) 
find results in Wisconsin lakes similar to those obtained by 
Lebedinzeff in the Caspian and Black seas, and the same 
problem, in general, presents itself for solution, viz.: what 
is the relation of dissolved gases to alge or submerged 
aquatics; first, as to life and death, or continuity; second, 
as to periodicity or rate of reproduction; third, as to habit, 
or morphologic adaptation to environment? 
Pfeffer (00) remarks that currents of water are of the 
utmost importance in providing aquatic plants with con- 
tinual supplies of dissolved carbonic acid. Owing to the 
marked solubility of the latter a given volume of water can 
hold a higher percentage than is present in the supernatant 
air, while still more may be held in the form of dissolved 
carbonates. Indeed, according to Hassak (’88), a green plant 
is not only able to obtain carbon-dioxide from calcium 
bicarbonate, Ca(HCOs)2, but also can make use of 70% of 
the carbon-dioxide contained in sodium bicarbonate. This 
agrees with the investigations of Darwin and Pertz (’96), 
who showed by laboratory experiments that in water that 
is kept stirred, photosynthesis is about twice as vigor- 
ous as in water that is allowed to remain quiet. This had 
to do only with the removal of excreted oxygen, whereby 
its accumulation in the plant tissues is prevented. This 
fact added to the benefits derived from a constant renewal 
