DISCUSSION OF RESULTS. 49 



RELATIVE IMPORTANCE OF PLANKTON CONSTITUENTS IN 

 PRODUCING MAXIMA. 



In Lake Winnebago and shallow lakes of a similar type it ia 

 evident that the great maxima are produced by plants. We 

 have found in the discussion of the Lake Winnebago plankton 

 that certain cladocera, like Eurycercus, sometimes form an im- 

 portant part of the plankton, but it may be said generally that 

 all large maxima are dependent for their size on plants. 



In deep lakes of the type of Green lake, the Crustacea, as com- 

 pared with the plants, are much more abundant than in the shal- 

 low lake, but even here, too, the plants, especially the diatoms, 

 are to a considerable extent responsible for the maxima. This 

 is shown very strikingly in the March maxima of Green lake. 



It will be noticed, too, that when Crustacea are largely imr 

 portant in producing plankton maxima, it is not as a rule the 

 result of the development of a single kind, but the result of the 

 simultaneous development of several kinds. 



In the discussion of the total plankton of the lakes in the 

 northern part of the state, I have stated that the August plank- 

 ton of the shallow r lakes in successive years is more uniform than 

 that of the deep lakes. This is explained, I think, by the 

 greater relative importance of the Crustacea in the deep lakes, 

 for there is greater variation in the maxima of the Crustacea 

 than in those of the "bloom." In plankton collections cover- 

 ing a period of years, we may expect the curves for the shallow 

 lakes to show much greater uniformity than those of the deep 

 lakes because of the greater importance of the vegetable part 

 of the plankton. 



COMPARISON OF PLANKTON AND TEMPERATURE CURVES. 



The temperature curves of the lake waters are similar to the 

 mean curves of the localities in which the lakes are situated, 

 with of course fewer variations and with a summer maximum at 

 a somewhat later period. The summer maximum of the sur- 



