154 WISCONSIN PHYTOPLANKTON 



var. PLATYDISCA G. M. Smith. PL 39, Figs. 1-3. 

 Trans. Wis. Acad. Sci., Arts, & Lett. IS 2 : 451, pi. 30, figs. 101-105. 1916. 



Colonies always flat, generally 8-celled. Cells oblong-elliptic and 

 arranged in a double series. Coenobia with small interstices between 

 the cells. (Facultative Planktont). 



Cells 4.5-7.5 //, broad, 8-17 p, long. 8-celled coenobia 11-30 p. broad, 

 18-30 p. long. 



Camp (rrr), Eagle (rr), Fowler (rr), George (rr), Horse (rrr), Kegonsa 

 (ss), Paddock (rr), Pine (1) (rr). 



An alga that has been considered a normal variation of S. bijuga but 

 one which, as stated elsewhere (1. c.), seems more closely related to 

 8. arcuatus. 



SCENEDESMUS ACUTiFORMis Schroder. PI. 39, Figs. 4-6. 

 Forschungsbr. a. d. Biol. Stat. zu Plon 5: 45, pi. 2, figs. 4*-4b. 1897. 



Coenobia flat, of 2-4-8 (generally 4) cells arranged in a linear series. 

 Cells fusiform, with acute apices. Cell wall of interior cells with a 

 single ridge that extends from pole to pole on each side; wall of termi- 

 nal cell with 2-4 ridges. Poles of cells without spines or teeth. (Fac- 

 ultative Planktont). 



Cells 5-8 n broad, 16-22 p. long. 4-celled colonies 16-22 //. broad, 

 20-25 p. long. 



Mendota (rr), Rice (1) (rrr). 



Only a single longitudinal ridge can be seen in a front view of the 

 cell but the number of ridges is readily ascertained in an end view of 

 cells. The presence of these ridges without accompanying spines or 

 teeth separates this from other species. 



SCENEDESMUS ARMATUS (Chodat) G. M. Smith. PI. 39, Figs. 7-10. 

 Trans. Wis. Acad. ,Sci., Arts, & Lett. 18 J : 460, pi. 29, figs. 90-93. 1916. 



Coenobia of 2-^4-8 cells arranged in a linear or subalternating series. 

 Cells ovoid to oblong-ellipsoid; with rounded apices. Terminal cells 

 with a single long spine at each pole. Both sides of cells with a longi- 

 tudinal ridge that may extend from pole to pole but is generally indis- 

 tinct in the median portion of the cell. (Facultative Planktont). 



Cells 4-7 p. broad, 7-16 p. long. 4-celled coenobia (without spines) 

 7-16 p. broad, 16-25 p. long. Spines 5-7 p, long. 



Bear (2) (rr), Bear Trap (rrr), Bone (rr), Browns (rr), Carson (rr), Fish- 

 trap (rrr), Horseshoe (2) (rr), Lac Court Oreilles (rr), Little Butternut (rrr), 

 Little Crooked (rr), Loveless (rr), Lynx (rrr), Mendota (rrr), Pardee (rrr), 

 Pine Tree (rr), St. Croix (rrr), Silver (rr), Upper Turtle (rrr), Wolf (rr). 



