300 FRESH-WATER ALG^E OF THE UNITED STATES. 



LYNGBYA RUPESTRE, ( Ag. ) Kg. 



Stratum compact, rather velvety, gelatinous, shortly radi- 

 ating, bright blue green, or becoming dark steel blue, the 

 lower strata becoming discolored and fibrillose ; trichomes 

 rigid, rather flexuous, a little torulose towards the apex ; 

 articulations equal, or nearly equal in length and breadth ; 

 very finely punctate, extreme apex paler or colorless. 



Diameter of filaments, 7-8 /^. 



Syn. Phormidium rupestre, Kg. ; Oscittaria rupestris, Ag. 



Plate CCII, figs. 5-8, from specimens collected by J. D. 

 Smith, on rocks, falls of Deep Creek, Maryland. 



LYNGBYA SUBTORULOSA, (Breb.) Wolle. 



Forming a firm, aeruginous- steel color, membranaceous 

 stratum; trichomes ' rather straight, subtorulose, pale aeru- 

 ginous ; articulations nearly equal in length and breadth, 

 the joints somewhat contracted and hyaline. Sheath firm, 

 granulate and niucose. 



Diameter of filaments, 7-8 /*. 



Syn. Phormidium subtorulosa, Breb. ; Ph. lacustre, Naeg. 



From moist grounds, Florida. 

 Plate CCII, figs. 3, 4, Florida. 



LYNGBYA MEMBRANACEA, (Kg.) Thur. 



Forming a firm leather-like expanded stratum, blackish 

 brown or olivaceous color. Filaments distinctly articulate. 

 Articulations before division as long or one-half longer than 

 wide ; light aeruginous or light brown ; end cells slightly 

 attenuate, sheath colorless and thin. 



Diameter filaments, 4-9 /u. 



.Kirchner finds two forms which he denominates genuina 

 and inaequalis. The former, with filaments of nearly uniform 

 thickness ; the other verv variable in size. 



/ */ 



Syn. Phormidium membranaceum, Kg. 



Collected by F. Hosford, Charlotte, Vermont. 

 Plate CCI, figs. 11-13. 



LYNGBYA VULGARIS, (Kg.) Kirch. 



Stratum thin, inore or less expanded, mucilaginous, dark 

 steel blue, purplish, olive, brown or turning yellow, opaque 

 or shining ; by age becoming thickened ; trichomes straight, 

 rigid, distinctly sheathed, joints as long as broad or shorter ; 



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