Lyngbya contorta Lemmermann 1898, p. 202 

 PL 112, Fig. 1 



Plants solitary and planktonic, spirally twisted or coiled (rarely 

 straight); trichomes not tapering at their apices and without con- 

 strictions at the cross walls; cells 1.5-2/,t in diameter, 3.5-5.6;a long; 

 sheaths thin but firm. 



This plant sometimes becomes dominant in the plankton of a 

 hard water lake and so abundant as to color the water a brownish- 

 green or a rusty-gray. In some small Iowa lakes it has been found 

 in almost pure growth with scarcely any other phytoplanktonic spe- 

 cies present. The dispersed habit of the plant and its failure to 

 agglutinate account for its inability to produce the unbalanced con- 

 ditions produced by other blue-green plankters. 



Eu- and tychoplanktonic. Wis. 



Lyngbya Diguetii Gomont in Hariot 1895, p. 169 

 PL 112, Fig. 8 



Plants solitary or entangled, sometimes forming bundles, fre- 

 quently adhering to and growing out from filamentous algae which 

 have non-mucilaginous walls; filaments up to 3.2/* in diameter, 

 sheaths thin; trichomes 2.5-3/i, in diameter, cells 1.5-3.5/i long; 

 apical cell convex, smooth. 



This is a very common species in hard water habitats and is in- 

 variably found associated with Cladophora and Rhizoclonium. It 

 is similar in some characters and in habitat to Lyngbya epiphytica 

 Wille (Nyt Mag. f. Natur., 1913, p. 25), a synonym of L. Nord- 

 gaardii Wille, but in our region is slightly larger than that species. 



Mich., Wis. 



Lyngbya epiphytica Hieronymus in Engler & Prantl 1900, p. 67 



PL 112, Figs. 2, 3 



Plants epiphytic, entangled and spirally twisted about other 

 filamentous algae to which they are adjoined throughout their en- 

 tire length; filaments 1.5-2.5/x in diameter; trichomes without con- 

 strictions at the cross walls; cells 1.2-2/x in diameter, 1-2 fi long; 

 apical cell convex, not capitate; sheath thin and close. 



This species is not to be confused with L. epiphytica Wille, which 

 is synonymous, apparently, with L. Nordgaardii Wille ( Fremy, Soc. 

 Arch, et Hist. Nat. Manche, 47, p. 44, 1936). 



On filamentous algae. Tychoplankter. Wis. 



[500] 



