12. Cells fusiform, oblong or ovate, straight or nearly so - 13 



12. Cells strongly curved - ^^ 



13. Cells 15-20fi in diameter....- — - - C. acuminatum 



13. Cells 4-8^ in diameter C. ambiguum 



14. Stipe stout and tubular, with irregular margins.... ._ .- C. curvatum 



14. Stipe long and slender... C. falcatum 



Characium acuminatum A. Braun in Kuetzing 1849, p. 892 



PI. 46, Fig. 7 

 Cells oblong or narrowly ovate, narrowed anteriorly to form a 

 short apiculation, acuminate; stipe short; cells 15-20/a in diameter, 

 35-40ju long. 



Attached to filamentous algae. Mich., Wis. 



Characium ambiguum Hermann 1863, p. 26 



PI. 45, Fig. 11 



Cells solitary, lance-shaped, fusiform or ensiform, narrowed to a 



sharp point anteriorly, tapering posteriorly to a fine hair-like stipe, 



without an attaching disc; chloroplasts 1-3; cells 4-Sfx in diam.eter, 



25-30;u long. 



Attached to filamentous algae; tychoplanktonic. Mich., Wis. 



Clmracium curvatum G. M. Smith 1918, p. 641 

 PI. 45, Figs. 12, 13 

 Cells lunate or sickle-shaped, either sharply or bluntly pointed; 

 stipe stout, without an attaching disc; chloroplast with or without 

 a pyrenoid; cells 3-6/x in diameter, 13-22jtA long, including stipe. 

 Epiphytic in the mucilage of colonial algae; tychoplanktonic. Wis. 



Characium Debaryanum (Reinsch) DeToni 1889, p. 628 



PI. 46, Fig. 19 

 Cells oblong or ovoid, broadly rounded anteriorly, narrowed 

 below into a stout stipe with a basal adhesive disc or swelling; cells 

 20-25jLi in diameter, 30-40/x long. 

 Epizoic on copepods. Mich. 



Characium falcatum Schroeder 1898, p. 23 

 PI. 45, Fig. 14 

 Cells sickle-shaped, ending in a long sharp point; stipe long and 

 slender, without an attaching disc; 1 chloroplast without a pyrenoid 

 ( ? ) ; cells 4.2-6.5/u, in diameter, 36-50/i, long. 



This species is somewhat like C. rostratum but is separable on the 

 basis of the attaching disc which that species possesses. Also, C. 



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