f3 of their lateral walls S. opoliensis 



14. Cells cylindrical or ovate, adjoined along 



their entire lateral walls S. quadricauda 



14. Cells naviculoid or subquadrate, not adjoined 

 along their entire lateral walls 15 



15. Cells naviculoid, attached along the middle 



% 



15. Cells subquadrate, lateral walls of inner cells 

 concave; attached only at the corners S. perforatus 



16. Spines arising from both the poles and from face of cell S. ahundans 



16. Spines arising from the poles of the cell only 17 



17. Cells naviculoid, narrowed at the poles S. opoliensis 



17. Cells oblong or cylindrical, the ends rounded S. longtis 



18. Outer cells only bearing a long spine at each pole S. armatus 



18. All cells bearing 2 or 4 sharp teeth at the poles S. hrasiliensis 



Scenedesmus abundans ( Kirch. ) Chodat 1913, p. 77 



PI. 61, Fig. 21 

 Cells oblong or ovate, in a linear series of 4, the terminal cells 

 with 1 or 2 polar spines and 2 spines on the lateral wall, the inner 

 cells with a spine at each pole; cells 4-7 /x in diameter, l-12fx long. 

 Plankter; found in several lakes; common. Mich., Wis. 



Scenedesmus abundans var. asijmmetrica ( Schroed. ) 

 G. M. Smith 1916a, p. 468 

 PI. 61, Figs. 22,23 

 Cells oblong-ellipsoid, outer cells with a spine at each pole and 

 all cells with a median spine arising perpendicularly from the lateral 

 walls; cells 2.5-4.5/x in diameter, 12-15/x long. 

 Plankter; uncommon. Wis. 



Scenedesmus abundans var. brevicauda G. M. Smith 1916a, p. 468 



PL 61, Figs. 26, 27; PI. 62, Fig. 1 

 Cells smaller than the typical; spines shorter and fewer; cells 

 2.5-5;u in diameter, 5-8/i, long; spines 1.5-3.5;Lt long. 

 Wis. 



Scenedesmus abundans var. longicauda G. M. Smith 1916a, p. 467 



PL 62, Figs. 4,5 

 Cells smaller than the typical, with relatively longer spines; cells 

 3-6/x in diameter, 7-9/i, long; spines 6-lOyu. long. 

 Wis. 



Scenedesmus abundans var. spicatus (West & West) 

 G. M. Smith 1916a, p. 468 

 Colony composed of 2-4 cells, the outer cells with a longitudinal 

 series of 5-7 spines, the inner cells with 1-2 spines at the apices 

 only; cells 4ju, in diameter, 7.5-9/x long. 



Wis. 



[274] 



