106 



PLANKTON OF WISCONSIN LAKES 



Fig. 37. — The quantity of dry organic matter in the net plankton of Lake 

 Monona in 1913 and 1916, and in the nannoplankton in 1916. Curve A 

 represents the net plankton in 1913, curve B the net plankton in 1916 and 

 curve C the nannoplankton in 1916. The amounts are indicated in milli- 

 grams per cubic meter of water. See tables 45 and 46. 



The ratio of the organic matter to the total nitrogen in the net 

 plankton of Lake Monona varied from 8.5 to 14,6. (See table 45.) 

 In three-quarters of the samples upon which nitrogen determinations 

 were made, however, the ratio fell between 9 and 12, thus showing a 

 fairly constant proportion of nitrogen in the organic matter. The pro- 

 portion was larger in the samples collected in 1915 than in those of any 

 other year ; in only one sample obtained in this year did the nitrogen 



