SUMMARY AND DISCUSSION 149 



pentosans 4.57 per cent, and the crude fiber 5.32 per cent. Using the 

 crude protein value of the nitrogen these four substances account for 

 61.9 per cent of the organic matter, leaving 38.1 per cent as undeter- 

 mined nitrogen free extract. 



For the deep part of Lake Mendota the mean quantity of dry organic 

 matter in the total plankton amounts to approximately 435 kilograms 

 per hectare (338 pounds per acre) ; the monthly variations in the quan- 

 tity of organic matter are shown graphically in figure 36. The amount 

 varied from a minimum of 256 kilograms per hectare (228 pounds per 

 acre) in February to a maximum of 522 kilograms per hectare (465 

 pounds per acre) in December. 



When the volume and the area of the entire lake are taken into 

 account the average amount of organic matter in the standing crop of 

 total plankton is 240 kilograms per hectare (214 pounds per acre). 

 Crude protein and ether extract make up a little more than 52.0 per 

 cent of this organic material. 



Lake Monona, The mean quantity of organic matter in the total 

 plankton of Lake Monona is 3,163 milligrams per cubic meter of 

 water, of which 9.21 per cent consists of nitrogen (57.56 per cent of 

 crude protein), 5.36 per cent of ether extract, 4.74 per cent of pento- 

 sans, and 4.35 per cent of crude fiber. The crude protein and the three 

 non-nitrogenous substances that were determined make up 72.01 per 

 cent of the organic matter, while the remainder consists of undeter- 

 mined nitrogen free extract. 



In the deep water area of the lake the average amount of dry 

 organic matter in the standing crop of total plankton is a little more 

 than 665 kilograms per hectare (594 pounds per acre), while the yield 

 of the whole lake is about 267 kilograms per hectare of surface (238 

 pounds per acre). 



Lake Wauhesa. The 16 samples of total plankton from Lake Wau- 

 besa gave an average of 4,398 milligrams of dry organic matter per 

 cubic meter of water. The mean percentage of nitrogen in this ma- 

 terial is 7.78 per cent, of ether extract 4.61 per cent, of pentosans 

 5.76 per cent, and of crude fiber 4.41 per cent. (Table 25.) By con- 

 verting the nitrogen into crude protein these four substances account 

 for 63.4 per cent of the organic matter, leaving 36.6 per cent as un- 

 determined nitrogen free extract. 



The average quantity of dry organic matter in the standing crop of 

 total plankton is 503 kilograms per hectare (448 pounds per acre) for 

 the area bounded by the 10 meter contour line, while the yield of the 

 entire lake is 241 kilograms per hectare of surface (215 pounds per 

 acre) . 



In what has been designated as the deep water portions of the three 

 lakes the total plankton of Monona gives the largest average amount of 



