12 PLANKTON OF WINNEBAGO AND GREEN LAKES. 



Melosira. 



Melosira is found in very small numbers in Green lake, and 

 no inferences can be drawn as to its annual distribution. 



In Lake Winnebago its appearance seems somewhat erratic, 

 but there is evidence of two maxima, one in May, and one in 

 September. 



Synedra, pulchella Kiitz. 



Synedra pulchella occurs in Lake Winnebago in 'all the 

 months of the year. In 1900 there was evidence of a spring 

 maximum in May and a fall maximum in October. In the 

 other years there was no pronounced increase at any time. 



In Green lake it is practically absent in July and August, 

 and only few are found in September, October, and Novem- 

 ber. Large numbers are present in December, January, and 

 February, and there is another increase in April and May. 



Synedra acus var. delicatissima Grun. 



This variety occurs in both Green lake and Lake Winnebago, 

 but in much greater abundance in Green lake. I have found 

 it in Lake Winnebago in February, March, April, and June. 



In Green lake I have found it in nearly every month of the 

 year, but it is in the winter that it especially flourishes, being 

 very numerous from January to May. With Asterionella it 

 forms one of the most important elements of the winter plank- 

 ton of Green lake. 



Fragilaria. 



I have not found Fragilaria in Lake Winnebago in July, 

 August, September, or October, and only once have I found it 

 at any time very abundant, that was in the middle of May, 

 1900. 



In Green lake it occurs at the same times, my only large col- 

 lection being at the middle of May, 1901. 



