Wood.] If^^ [June 18, 



black color ; filaments flexuous, flexible, almost 0.25" long, irregularly 

 branched, their surface smooth ; branches elongate, single, rarely in 

 pairs, free, sometimes fuscous, frequently hyaline, their apices generally 

 truncate, rarely somewhat attenuate, frequently provided with enlarge- 

 ments, never reddish ; cytioplasm aeruginous, very thin, generally dis- 

 tinctly articulate ; articles mostly shorter than broad, but sometimes 

 longer, frequently disjoined, often subglobose ; sheaths thick and firm ; 

 heterocysts both basal and interjected, single, extremely rarely gemi- 

 nate. 



Hab. In flumine Niagara prope cataractam. 



S. COETEX. Sp. Nov. 



S. minutissimum, stratum tenue submembraneum formante ; tricho- 

 matibus sparse pseudoramulosis, pseudoramulisque repentibus et plus 

 minus concretis, viridibus aut dilute fuscis, varie curvatis, baud rigidis ; 

 cytioplasmate viride, articulato, rare distincte granuloso ; articulis diam- 

 etro longioribus aut brevioribus ; vaginis arctis, nonnihil tenuibus, 

 achrois, plerumque coloris expertibus, sed interdum dilute fuscis ; cellulis 

 perdurantibus et singulis et geminis, et basalibus et interjectis, globosis 

 vel subglobosis. 



S. Very minute, forming a thin, submembranaceous stratum ; fila- 

 ments sparsely branched, together with the branches, creeping and more 

 or less concreted together by their sides, green or light brown, variously 

 curved, not rigid ; cytioplasm (internal filament) articulate, rarely dis- 

 tinctly granulate ; joints longer or shorter than broad ; sheaths close, 

 rather thin, transparent, generally colorless but sometimes light brown ; 

 heterocysts globular or subglobular, single or in pairs, basal or other- 

 wise. 



Diam.trich. cum vag. ^^^^"_^^z^ui, 



Hab. South Carolina in ramis (Platanus occidentalis). Prof. Ravenel. 



S. KAVENELLII.* Sp. NoV. 



S. lignicola, breve caespitosum, viride-nigrum ; trichomatibus plerum- 

 que repentibus, vel fusco-olivaceis vel aureo-fuscis, modice pseudoramosis; 

 ramis ascendentibus, rigidis, flexuosis rare pseudoramulosis, vel fusco- 

 olivaceis vel aureo-fuscis, rarissime cum apicibus subachrois ; trichomati- 

 bus internis coloris expertibus, granulosis, saepe vagina erumpentibus, 

 plerumque articulatis ; articulis diametro longioribus aut brevioribus ; 

 vaginis arctis, crassibus, fusco-olivaceis vel aureo-fuscis, plerumque supra 

 truncatis et apertis, superficie nonnunquam irregulare ; cellulis perduran- 

 tibus subquadratis, singulis, interjectis. 



S. Forming little, shortly turfy spots, on bark, of a greenish color ; 

 filaments mostly creeping, either brownish olive or yellowish brown, 

 moderately branched ; branches ascending, rigid, flexuous, very rarely 

 provided with secondary branchlets, either brownish olive or yellowish 



* It affords me great pleasure to dedicate this species to Prof. H. W. Ravenel as an acknowledg- 

 ment, not so much of the aid rendered in my studies of our fresh water algae, as of his great ser- 

 vices to science in some of her kindred branches. 



