SUMMARY AND DISCUSSION 147 



organic matter 8.92 per cent consisted of nitrogen, 4.82 per cent of 

 ether extract, 4.36 per cent of pentosans, and 4.76 per cent of crude 

 fiber. With the exception of that for crude fiber, these percentages are 

 smaller than those of the corresponding samples of net plankton. The 

 crude protein, ether extract, and crude fiber constitute 65.33 per cent 

 of the dry organic matter in the average crop of nannoplankton of 

 Lake Monona; the remainder, 34.67 per cent, is represented by the 

 nitrogen free extract, of which 4.36 per cent consists of pentosans. The 

 percentage of nitrogen in the average standing crop of nannoplankton 

 of Lake Monona is considerably larger than that in the nannoplankton 

 of Lake Mendota, but the percentages of ether extract, pentosans, and 

 crude fiber are larger in the material from the latter lake. 



For the area bounded by the 20 meter contour line in Lake Monona, 

 the average quantity of organic matter in the nannoplankton amounts 

 to 494 kilograms per hectare (441 pounds per acre), with a variation 

 ranging from 140 kilograms to 1,198 kilograms per hectare (125 pounds 

 to 1,069 pounds per acre). For the entire body of water the mean quan- 

 tity of organic matter is 198 kilograms per hectare (177 pounds per 

 acre), with a minimum of 56 kilograms and a maximum of 480 kilo- 

 grams per hectare (50 pounds to 428 pounds per acre). 



Lake Waubesa. The average amount of dry organic matter in the 

 16 samples of nannoplankton from Lake Waubesa is 3,299 milligrams 

 per cubic meter of water, of which 7.92 per cent consists of nitrogen 

 (equivalent to 49.50 per cent of crude protein), 4.00 per cent of ether 

 extract, 5.55 per cent of pentosans, and 4.45 per cent of crude fiber. 

 (Table 25.) The crude protein, ether extract, and crude fiber consti- 

 tute 57.95 per cent of the organic matter in the nannoplankton mate- 

 rial, leaving 42.05 per cent to be classed as nitrogen free extract, of 

 which 5.55 per cent consists of pentosans. 



Unlike the material from the other two lakes the mean percentage 

 of nitrogen is higher in the nannoplankton than in the net plankton of 

 Lake Waubesa. The mean percentage of crude fiber is slightly larger 

 in the nannoplankton, but the percentages of ether extract and of pen- 

 tosans are larger in the net plankton. In comparison with the other two 

 lakes the mean percentage of nitrogen in the nannoplankton material 

 from Lake Waubesa is lower than that of Lake Monona and higher 

 than that of Lake Mendota; the percentage of ether extract is lowest in 

 the material from Waubesa, while the mean percentage of pentosans 

 and of crude fiber is highest in the material from this lake. 



Within the area bounded by the 10 meter contour line (p. 139) the 

 mean quantity of dry organic matter in the nannoplankton amounts to 

 336 kilograms per hectare (300 pounds per acre). The range of varia- 

 tion is from a minimum of 81 kilograms to a maximum of 625 kilograms 



