52 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
to account for the difference in gas content. These samples, with the excep- 
tion of those taken from Spectacle Pond July 30 and from the State Bog 
August 10, were all taken in clear weather in shallow water near shore. The 
bottom of Spectacle Pond is clean white sand and the water very clear. In 
Cedar Pond the water is clear but the bottom is muck, consisting of vegetable 
matter most of which is well decomposed. The water in the ditches of the 
State Bog is discolored, of a very dilute coffee color as viewed by transmitted 
light, and the bottom is muck as in Cedar Pond. Spectacle Pond, moreover, 
has very little vegetation, which accounts for the almost constant oxygen and 
carbon dioxide content from day to day or between day and night periods. 
On the other hand. Cedar Pond is well filled with water lilies and other 
vegetation which modifies the oxygen and carbon dioxide content of the 
water materially through respiratory and photosynthetic activities. In the 
State Bog ditches a more or less abundant growth of algae is found which 
brings about the same result. Accordingly, both in Cedar Pond and in the 
ditches of the State Bog a wide variation in carbon dioxide and oxygen 
content of the water is observed between day and night or between a clear 
and a cloudy day. Where the vegetation is denser the variation is more 
pronounced. 
Table i. Variation in oxygen and carbon dioxide content of waters at East Wareham, 
Massachusetts 
Source 
Date, 
1918 
Weather 
Hour 
Temo. 
c' 
Carbon Dioxide 
Cc. per Liter 
Oxygen Cc 
per Liter 
Ditch, State Bog 
July 
^3 
Clear 
9:00 A.M. 
24° 
10. 1 
0.9 
11:00 A.M. 
25 
3.6 
2.5 
3:00 P.M. 
26.5 
2.0 
4.9 
29 
9:00 A.M. 
25 
6.4 
2.4 
11:00 A.M. 
27 
5-2 
3.6 
2:30 P.M. 
29 
4.5 
4:00 P.M. 
29-5 
4.0 
Aug. 
10 
Cloudy 
11:00 A.M. 
20 
5-1 
1.8 
1:45 P.M. 
20.5 
3-9 
3.6 
Spectacle Pond 
July 
15 
Clear 
9:00 A.M. 
21° 
0.7 
6.1 
11:00 A.M. 
22 
0.7 
6.1 
< < 
3:00 P.M. 
24 
0.4 
6.1 
17 
10:30 A.M. 
24 
0.3 
6.1 
3:00 P.M. 
26 
0.2 
6.5 
Cloudy 
9:00 A.M. 
25 
0.3 
54 
( < 
11:00 A.M. 
26 
0.2 
54 
< < 
2:30 P.M. 
26 
0.1 
5.7 
< ( 
< < 
4:00 P.M. 
26 
0.1 
5.9 
Cedar Pond 
Aug. 
I 
Clear 
9:30 A.M. 
22 
0.5 
4-5 
22 
0.5 
4.9 
3:00 P.M. 
29 
0.4 
51 
29 
045 
5.5 
" " (east end) 
6 
9:30 A.M. 
22 
2.8 
3.3 
4:00 P.M. 
27 
I.I 
4.8 
The carbon dioxide content of the water in Cedar Pond and in the ditches 
