Jan., 1921] 
BERGMAN — OXYGEN CONTENT OF WATER 
55 
this experiment. This is due to the presence of algae in the water, since 
these plants during the day were actively giving off oxygen and were using 
it up during the night in respiration. The lack of vegetation in Spectacle 
Pond accounts for the uniformity of the oxygen content as between day and 
night, the slight changes occurring being due mostly to the difference in 
temperature. 
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Fig. 2. Oxygen content of water from Spectacle Pond, East Wareham, Massachusetts, 
and of water from Spectacle Pond held in tubs under experimental conditions, 1919. 
From this experiment it is evident that injury occurred only to the 
plants in the shaded tubs, the water of which shows a great reduction below 
the oxygen content of either pond or ditch water (figs. 2 and 3). As the 
oxygen content was the only factor which was changed extensively through- 
out the experiment, the injury must be attributed to the lack of oxygen. 
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Fig. 3. Oxygen content of water in ditch of State Experiment Bog, East Wareham, 
Massachusetts, and of water from the ditch held in tubs under experimental conditions, 1^19. 
