ORGANIC CONTENT OF LAKE WATER 
193 
PLANKTON 
In the study of the forms of soluble nitrogen the plankton was extracted from 
the water by the centrifuge; it was dried and weighed, and the organic matter and 
nitrogen were determined. The quantities were too small to permit other determi- 
nations, such as ether extract. The amounts of nitrogen from these samples already 
have been published (nitrogen report, pp. 273, 282), but the other data appear here 
for the first time. The “ash” of these specimens ought rather to be called “total 
inorganic matter,” for it is composed in large part of minute particles of silt that 
remain suspended in the water and are removed by the centrifuge. This subject 
is discussed in the plankton report, page 80. 
Table 6. — Plankton, milligrams per liter 
Date 
Depth, 
meters 
Total 
plankton 
Ash 
Total 
organic 
Nitrogen 
LAKES 
Mendota 
Oct. 18,1922 
0 
3.23 
1.98 
1. 25 
0. 105 
Do 
Dec. 5, 1922 
0 
3. 20 
1. 47 
1. 73 
.144 
Do 
Feb. 28,1923 
0 
1.62 
.74 
.88 
.052 
Do ._ 
July 24,1923 
0 
4. 60 
1.23 
3. 37 
. 113 
Do 
Sept. 21, 1923 
0 
4.06 
2. 00 
2. 06 
.091 
Do 
Oct. 24,1923 
0 
3. 90 
2.08 
1.82 
.045 
Do 
Apr. 23,1924 
0 
1.96 
1.01 
.95 
.080 
Do 
June 18. 1924 
0 
2. 12 
.80 
1. 32 
.092 
Do 
July 21, 1922 
20 
2. 12 
1. 43 
.69 
.050 
Do 
Sept. 26, 1922 
20 
3. 60 
2. 75 
.85 
.047 
Do..._ 
Feb. 28,1923 
20 
2.45 
1. 68 
.78 
.057 
Do 
July 24,1923 
20 
3. 42 
1.93 
1. 49 
.058 
Do 
Sept. 21, 1923 
20 
4. 62 
2. 34 
2.28 
.098 
Do 
June 25. 1924 
20 
1.84 
1.00 
.84 
.045 
Mean _ 
3. 05 
1. 60 
1.45 
.077 
Bass 
Dec. 20,1923 
0 
1.08 
.51 
.57 
.034 
Devils 
July 11,1923 
0 
1. 30 
.88 
.42 
.015 
Do 
Oct. 27,1922 
0 
.86 
.47 
.39 
.038 
Geneva 
July 16,1923 
0 
2. 18 
.93 
1. 25 
.051 
Green 
July 18,1923 
0 
2. 18 
1.25 
.93 
.042 
Do 
Oct. 16,1923 
0 
2.05 
1.16 
.89 
.049 
Kegonsa 
July 20,1923 
0 
22. 30 
3.02 
19.28 
.697 
Madeline 
Dec. 12,1923 
0 
2. 26 
.52 
1. 74 
.096 
Michigan 
Feb. 28,1923 
0 
4. 38 
2.76 
1. 62 
.020 
Monona 
June 28, 1923 
0 
7. 20 
2.00 
5. 20 
.389 
July 6, 1923 
0 
1. 66 
.64 
1.02 
.073 
Turtle 
Jan. 18, 1924 
0 
1.40 
.66 
.74 
.030 
Waubesa... 
July 20,1923 
0 
10. 12 
1.97 
8. 15 
.299 
Wingra 
June 26, 1923 
0 
25.72 
8. 51 
17. 21 
.882 
RIVERS 
Wisconsin 
July 30,1923 
0 
7. 95 
5. 38 
2. 57 
.161 
Do.... 
Nov. 21, 1923 
0 
2.26 
1.25 
1. 01 
.053 
Yahara 
July 6, 1922 
0 
20. 12 
(>) 
(>) 
.609 
1 Not determined. 
