[Vol. 10 



414 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



South Free Peoples Lake. 



The coenobia were exactly similar to Snow's figure except that 

 they consisted of 16 cells instead of 32. Both Miss Snow's speci- 

 mens and those from North Dakota seem to differ from the 

 original form of Lemmermann in the straight and uncoiled form 

 of the coenobium. Lemmermann's figure (see G. M. Smith in 

 Trans. Wis. Acad. 18 : pi. 25, f. 16. 1916), shows that his form was 

 distinctly coiled in a spiral fashion, and G. M. Smith in his 

 Monograph of Scenedesmus (loc. cit., p. 446) has included this 

 character in his description of the variety. The same writer 

 {loc. cit., p. 446) makes some reference to the spiral form of 

 the coenobia in Miss Snow's work, but a careful examination 

 of her paper has failed to show that she makes any statement 

 concerning this character. Since her figures illustrate a per- 

 fectly straight colony, it has therefore been assumed that the 

 specimens from Lake Erie differed from those of Lemmermann 

 in exactly the same way as do those from North Dakota, in the 

 Btraight form of the coenobia. 



S. dimorphus (Turp.) Kiitz. 



Willow Lake; Dion Lake; Red Willow Lake. 



S. obliquus (Turp.) Kiitz. 



Mouth of Minnewaukon Bay, Devils Lake, below grade. 



S. quadricauda (Turp.) Br6b. 



Cut-off Pond, Stump Lake; Willow Lake; Spiritwood I, Bay; 

 Red Willow Lake; Carpenter Lake. 



Var. bicaudatus Hansg. ( = Sc. longus Meyen Smith, Wis. Acad. 

 Sci. Trans. 18: 469. 1915). PI. 21, fig. 5. 



Spiritwood I, Bay. 



Var. quadrispina (Chodat) G. M. Smith. 



Crow Lake. 



Var. Westii G. M. Smith. 



Crooked Lake. 



Genus crucigenia Morren 



Crucigenia quadrata Morren. 



Rare in the plankton of East Lake. 



C. tetrapedia (Kirchn.) W. & G. S. West. 



Rare in the plankton of Red Willow Lake. 



