22 FRESH-WATER ALGJR OF THE UNITED STATES. 



Hab. Common on damp earth. West Point, New York ; Bingluun, Massachusetts ; Provi- 

 dence, Rhode Island; Baily, Silliman's Journ., N. S., vol. iii. 



Terrestrial, stratum more or less expanded, deep aeruginous chalybeate, or olivaceous fuscous, 

 mucous membranaceous ; filaments equal, in filiform fasciculi, which are often much elongate 

 and penicillately exserted from the open common sheath ; joints as long as broad, the dissepi- 

 ments granulate ; the apex obtuse, straight. 



Genus LYNGBYA, AGARDH. 



Trichomata inarticulata vel breve articulata, cellulis perdurautibus instructa. Yaginse ssepe colo- 

 ratae, crassse, ssepe Iamellona3. 



Filaments not articulate, or shortly so, furnished with heterocysts. Sheaths often colored, thick, 

 often lamellate. 



"L. muralis, Aa. 



Filaments somewhat rigid, thickish, tortuous, very long, interwoven in a bright, grass-green 

 stratum; annuli strongly defined. Ag. Syst., p. 74 ; Harv. Man. Ed., p. 160; Conf. muralis. 

 Dillw., tab. 7, E. Bot. t. 1554. |3. aquatica. 



Hob. Var. j3. in pools of fresh water, Whalefish Island, Davis Straits. Dr. Lyall. 



The specimens are mixed with turfy soil. Except in the submerged habitat, this agrees with 

 the ordinary form. Intermixed with threads of the usual size and structure are others 

 cohering in pairs, as in L. copulala, Ilarv., which is obviously only a state of this widely 

 dispersed species. I have not received specimens of the ordinary L. muralis from America ; 

 but no doubt it is common on damp walls, &c., as in Europe generally." 



I have never identified this species, and have simply copied Harvey's account 

 of it from the Nereis Boreali Americana, pt. III. p. 104. 



I;, bicolor, WOOD. 



L. trichomatibus simplicibus, in csespites nigro-virides vel caaruleo-virides dense intricatis, varie 

 curvatis, plerumque inarticulatis, intcrdum breviter articulatis et ad genicula contractis; cytio- 

 plasmate dilute cseruleo-viride, plerumque copiose granulate, ssepe intcrrupto ; cellulis perdu- 

 rantibus cylindricis, ssepe elongatis, saturate brunnejs, sparsissimis; vagiuis firmis, achrois, in 

 trichomata matura modice crassis. 



Syn. L. bicolor, WOOD, Prodromus, Proc. Amer. Philos. Soc., 18G9, 124. 



Diam. T7 V 5 "- 



Hab. In flumine Schuylkill prope Philadelphia. 



L. with the filaments closely interwoven into a blackish or bluish-green mat ; filaments variously 

 curved, simple, mostly inarticulate, sometimes shortly articulate with the joints contracted ; 

 endochrome light bluish-green, mostly very granulate, often interrupted ; heterocysts cylin- 

 drical, often elongate, deep brown, very few; sheaths firm, transparent, in old filaments 

 moderately thick. 



Remarks. This species is abundant in the shallow water of the Schuylkill 

 River, near Spring Mills, where it forms dark waving tufts a half inch or more in 

 height, which are adherent either to the bottom of the stream or to some firm sup- 

 port, such as large growing plants, sticks fixed in the mud, &c. When examined 

 with the microscope, these tufts are seen to be composed of innumerable, very long, 

 motionless, greatly curved filaments. They do not seem to be attached to their 

 support, but in the denser parts are woven into a very thick mat, which apparently 

 adheres en masse to the fixed body. These filaments are very rarely articulate, 



