spaced bands of roughenings; colorless; extending far beyond the 

 apices of the trichomes. 



In a variety of lakes, both acid and hard water; in Sphagnum bogs. 

 Mich., Wis. 



Lynghya aestuarii ( Mert. ) Liebmann 1841, p. 492 

 PL 111, Fig. 8 



Plants aggregated, entangled, forming extensive layers on sub- 

 merged substrates, or upon moist earth and stones; sometimes be- 

 coming free-floating. Filaments varying greatly in diameter, 10-26/i, 

 wide. Trichomes 8-20- (28)//, in diameter, tapering a little at the 

 apices, which vary in shape, conical, truncate, or somewhat capitate. 

 Cells 2.5-5/A in length, not constricted at the cross walls. Sheaths 

 firm, becoming thickened, lamellose, and discolored with age. 



This species sometimes forms very thick, felt-like layers, yellow- 

 gray or olive-green in color, the color ordinarily masked by accumu- 

 lated silt and debris. 



On stones and moist earth. Mich., Wis. 



Lynghya Birgei G. M. Smith 1916, p. 482 

 PI. Ill, Fig. 9 



Plants solitary, planktonic, scattered among water bloom organ- 

 isms; filaments straight, (18)-24-(25)/x in diameter, with many 

 hormogonia when aged; sheaths thick and firm, not lamellated, ex- 

 tending far beyond the apices of the trichomes, which are broadly 

 rounded; trichome 20-24/x in diameter, not constricted at the cross 

 walls; cells very short and disciform, 3-7/a long. 



This species is frequently a prominent element in the composition 

 of water blooms which develop in lakes with a pH of 7.4-9.0. It is 

 almost invariably associated with Microcystis aeruginosa, Aphanizo- 

 menon fios-aquae, Anahaena flos-aquae, Stephanodiscus spp. and 

 Melosira spp. In fact, its association with these species in eutrophic 

 waters is so constant that during the months of July and August, 

 at least, the relative abundance of Lynghya Birgei G. M. Smith can 

 be used as an approximate index of alkalinity. Although abundant 

 in hard water lakes it does not play an important role in the water 

 bloom disturbances of which Aphanizomenon and Microcystis are 

 capable, because of its failure to form clots and floating masses. 



Common in the euplankton of many hard and semi-hard water 

 lakes. Mich., Wis. 



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