THE LIFE OF DEVILS LAKE 71 



clypeus, tho it is likely that all of the species in the lake are occa- 

 sionally driven from their natural habitat in the Ruppia zone 

 into the open water. 



The list of species follows. 



Chaetoceros elmorei. One of the characteristic phytoplanc- 

 tonts of the lake. It also frequently serves for the attach- 

 ment of other plauctonts such as Characium, Vorticella and 

 Cothurnia. It is of interest to note that this representative of a 

 marine genus should find in this brackish lake so favorable a 

 habitat that it now forms one of its characteristic species. 



The curve of seasonal distribution is given in pi. 16 which 

 shows that it is more limited in its occurrence than most of the 

 algae, seldom appearing before June, and disappearing about 

 December first. It has a distinct minimum about mid-August, with 

 maxima about the end of July and August, while in 1914 a second 

 sharp minimum occurred July 20. The few records from East Lake 

 show a much smaller number in Main Lake (fig. 17). 



Cyclotella. Three species of this genus, meneghiniana, striata 

 and comta occur in the Devils Lake complex. No attempt has been 

 made to differentiate them in the plancton counts. Cyclotella 

 occurs occasionally, tho rarely in winter, and rather frequently 

 at other seasons. In only one year (1913) is there evidence of a 

 rather definite maximum, which occurred in early September. 

 Meneghiniana has been found in Main, East and Spring Lakes 

 and in fresh water. Striata, which is typically a marine and 

 brackish water species, is reported from Main and East Lakes 

 and Lake P. Professor Elmore writes me that Devils Lake is 

 the only place where he has taken the latter species, altho it is 

 reported by Boyer from blue clay near Philadelphia. 



Stephanodiscus carconensis is widely distributed in the complex, 

 being reported by Elmore from Main, Mission, Stump and East 

 Lakes and Lakes C and P, altho he tells me that this is the only 

 region in which he has found it. He further states that it is not 

 given by Van Heurck (1896), and I have not found it in Schon- 

 feldt (i913), so it is evidently a rare species. Professor Elmore 

 reports it as common in Devils Lake in the plancton samples. 



Oyrosigma. Three species of Gyrosigma occur in Devils Lake, 

 of which kutzingii is common and the others rare. G. kutzingii Is 

 reported by Elmore from East and Mission as well as Main Lake, 

 and G. acuminatum from Main and Spring Lakes; while G. spen- 

 cerii is reported from Main Lake only in three collections. No 

 attempt has been made to differentiate the three species in the 

 plankton counts. The genus appears sporadically from April to 

 November, but the data are inadequate for drawing any conclu« 

 sions as to its seasonal distribution. 



