colony bearing a single long curved spine at each pole arising from 

 the corner of the cells, the outer lateral walls of the end cells 

 straight or umbonate; cells 3-3.5-(5)/i. in diameter, 10-13)u, long, 

 Mich. 



Scenedesmus quadricatida ( Turp. ) de Brebisson in 



de Brebisson & Godey 1835, p. 66 



PI. 64, Fig. 2 



Colony consisting of 2-4-8 oblong-cylindric cells usually in 1 



series (sometimes in 2 alternating series); outer cells with a long 



curved spine at each pole; inner cells without spines or with mere 



papillae at the apices; cells variable- in size, 3-18/x in diameter, 



9-35/x long. 



Common and widely distributed in a variety of habitats; one of 

 the most nearly ubiquitous algal species. Mich., Wis. 



Scenedesmus quadricauda var. longispina ( Chod. ) 

 G. M. Smith 1916a, p. 480 

 PI. 63, Fig. 22 

 A variety differing from the typical by the greater length of the 

 spines; cells 3.5-5|a in diameter, S-ll/x long; spines 7.5-10/i, long. 

 Plankter; in lakes. Mich., Wis. 



Scenedesmus quadricauda var. maximus West & West 1895, p. 83 



PL 64, Figs. 3, 4 



A variety differing from the typical by the larger size of cells 

 and relatively longer spines; cells 9-11.5/^ in diameter, 27-36/a long; 

 spines 20-30/a long. 



Plankter; in lakes; rare. Mich., Wis. 



Scenedesmus quadricauda var, parvus G. M. Smith 1916a, p. 480 



PI. 64, Fig. 6 



Colony composed of 2-16 cylindrical-ovate cells arranged in a 

 single series; outer cells with a long spine at each pole; inner cells 

 with spineless walls; cells 4-6.5/x in diameter, 12-17/x long. 



Very common in many lakes and swamps. Wis. 



Scenedesmus quadricauda var. quadrispina ( Chod. ) 



G. M. Smith 1916a, p. 480 



PI. 63, Fig. 21 



Colony composed of 4-8 ovate cells with short spines, usually 



strongly recurved; cells 4-7 A/x in diameter, 9-16/i, long; spines about 



3/x long. 



Rare, but widely distributed in many lakes and ponds. Mich., Wis. 



[ 280] 



