Ulothrix aequalis Kuetzing 1845, p. 197 

 PI. 6, Fig. 1 

 Filaments very long, composed of cylindrical cells and without 

 constrictions at the cross walls. Chloroplasts a parietal plate extend- 

 ing % of the distance around the wall. Cells 13-15.5yLt in diameter, 

 18-30^1 long. 



Common; forming pure, bright green masses in shallow water of 

 several lakes and swamps; scattered among other algae. Mich., Wis. 



Ulothrix cylindricum Prescott 1944, p. 349 

 PI. 6, Fig. 2 



Filaments long, curved, and Ughtly entangled. Cells elongate- 

 cyhndric, 11-12.5/x in diameter, 214 to 3 times longer than wide; the 

 wall thin and not constricted at the joints. Chloroplast a broad band, 

 nearly equal to the cell in length and folded around % of the cir- 

 cumference; pyrenoids 2-5. 



This species should be compared with Ulothrix aequalis Kuetzing, 

 which has thick walls, shorter cells, fewer pyrenoids, and a different 

 form of chloroplast. 



Tychoplankter. Wis. 



Ulothrix suhconstricta G. S. West 1915, p. 82 

 PI. 6, Fig. 11 



Filaments planktonic, composed of slightly inflated cells, which 

 are moderately constricted at the cross walls and sometimes inclosed 

 in a gelatinous sheath. Chloroplast a parietal plate extending 

 through about % of the median region of the cell, sometimes with a 

 pyrenoid. Cells 5.7-9/x in diameter, 10-36/i, long. 



Euplankter. Wis. 



Ulothrix suhtilissima Rabenhorst 1868, Alg. Exsic. No. 655 



PI. 6, Fig. 3 

 Filaments long and slender, free-floating or attached. Cells very 

 slightly inflated and constricted at the cross walls. Chloroplast ex- 

 tending the entire length of the cell, with 1 pyrenoid. Cells 4-5/x in 

 diameter, 11-14.8/x long. 



In shallow water of a swamp. Wis. 



Ulothrix tenerrima Kuetzing 1843, p. 253 

 PI. 6, Fig. 12 

 Filaments free-floating or attached; long, or in short sections; com- 

 posed of cylindrical, relatively short cells with constrictions at the 



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