Tolypothrix limbata Thuret in Bornet & Flahault 1887, p. 124 



•Pl. 126, Figs. 1, 2 



Filaments forming dense wooly tufts; coarse. Trichomes repeatedly 

 branched, the branches variously disposed, erect or spreading and 

 flexuous, rarely two unilateral branches arising from near the 

 base of a heterocyst. Cells quadrate or slightly longer than wide; 

 5.5-9/j, in diameter, 5-7 fi long; cell contents gray-green. Heterocysts 

 relatively large; globose; up to 11/x in diameter; occurring singly or 

 in pairs. Sheaths wide, thick, lamellated; becoming golden-brown 

 in age. 



This is a common species, usually entangled about or attached to 

 submerged aquatics; in tychoplankton in a variety of lakes. Mich., 

 Wis. 



Tolypothrix tenuis Kuetzing; emend. J. Schmidt 1899, p. 383 

 A long, slender, frequently and repeatedly branched trichome with 

 thin sheaths; either solitary or forming thick brown mats in full 

 development. Cells cylindrical, quadrate, or a little longer than 

 wide; 5-8/x in diameter, usually not constiicted at the cross walls. 

 Heterocysts subglobose to subcylindric; S/x in diameter, 11/x long; 

 occurring singly or 2-5 in a series. Sheath thin, firm, somewhat 

 swollen at the base of the branches. Filaments 8-10/i, wide. 



When young, the plants are attached in cottony masses about the 

 culms of rushes, later floating free. There often appears in our col- 

 lections an expression of this species which agrees with the descrip- 

 tion of T. tenuis var. Wartmanniana ( Kuetz. ) Hansgirg. 



This species appears in a great variety of lakes, commonly in 

 tychoplankton. Mich., Wis. 



DIPLONEMA Borzi 1917, p. 103 



A dichotomously branched, tortuous, radiating and prostrate tri- 

 chome inclosed in a hyaline or brownish sheath which may be 

 lamellated in the older portions, or homogeneous; the branches 

 arising near a heterocyst, which is globose or ovate, and either basal 

 or intercalary. Vegetative cells torulose or short-cylindric, much 

 constricted at the joints in the basal part of the trichome but with 

 parallel lateral walls in the distal portion, tapering slightly toward 

 the apex. 



Diplonema rupicola Borzi 1917, p. 103 

 PI. 126, Fig. 3 

 Characteristics as described for the genus; cells 3.2-4.5/t in diam- 

 eter, 3.5-5/A long; trichomes dichotomously branched in hyaline, 



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