4 Minnesota Algae 



II Sheaths hyaline, yellowish or brownish, often lamellose; cell contents 

 blue-green, rarely olive-brown, reddish-green, brownish-violet or copper-red. 



1 Cells not embedded in a gelatinous mass, mostly solitary among other 



algae 

 (i) Sheaths thick, distinctly lamellose; cell contents blue-green 

 A Sheaths colorless; cells 13-25 mic. in diameter 



C. turgidus 



B Sheaths yellowish or brownish; cells 5.8-11 mic. in diameter 



C. schizodermaticus 



(2) Sheaths not lamellose 

 A Cells 5-7 mic. in diameter C. minutus 



B Cells 1.7 mic. in diameter C. multicoloratus 



C Growing in hot water; cells 1-1.5 mic. in diameter 



C. thermophilus 



2 Cells embedded in a gelatinous mass, not free-floating 

 (i) Sheaths lamellose 



A Sheaths slightly lamellose; plants 4-8 mic. in diameter 



C. varius 



B Sheaths lamellose, finally irregularly peeling off; plants 6-1 1 mic. 

 in diameter C. decorticans 



(,2) Sheaths not lamellose, sometimes scarcely visible 



A Plants S mic. in diameter, mostly subquadrate, often triangular, 

 rarely multiangular; sheaths scarcely perceptible 



C. refractus 



B Plants 4-7.5, rarely 9 mic, in diameter, spherical 



C. helveticus 



C Plant mass pale yellowish; sheaths oblong-elliptical; cells 7.5-13 

 mic. in diameter; cell contents blue-green, yellowish or orange 



C. pallidus 



D Plant mass green, later becoming black; sheaths distinct, ellipsoid; 

 cells 2.7-6.6 mic. in diameter; cell contents blue-green 



C. cohaerens 



E Plant mass blue-green or olive; sheaths scarcely visible; plants 3-4 

 mic. in diameter; cell contents blue-green C. minor 



F Plant mass lead-colored or green becoming black; sheaths thick, 

 mucous; plants 3-8 mic. in diameter; cell contents blue-green 



C. membraninus 



3 Cells embedded in a gelatinous, free-floating mass 



(i) Plants 8-13 mic. in diameter, much crowded; cell contents green 

 or blue-green C. limneticus 



(2) Plants 13 mic. in diameter, usually in groups of two; groups lying 

 apart from each other; cell contents grayish-purple 



C. purpureas 



