FRESH-WATER ALGJE OF THE UNITED STATES. 59 



S. immersuin, Wood, (sp. nov.) 



S. immersum cum algis alteris intermixtum et plantas aquaticas adhaerens; trichomatibus 

 elongatis ; pseudoramulis plus minus distautibus, plerumque geminis, et e basi divergenter 

 adscendentibus, brevibus aut elongatis ; trichomatibus internis laste aerugiueis, interdum dis- 

 tincte articulatis, interdum inarticulatis, apice obtuse rotundato, serngineo; articulis diametro 

 subffiqualibus vel brevioribus ; vaginis amplis, hyalinis, coloris expertibus ; cellulis perdu- 

 rantibus distinctis, singulis, interjeetis, subcylindricis, diametro interdum fere duplo breviori- 

 bus, interdum duplo longioribus. 



Dtam.— Sin. vag. ^^^^^js" = -000415". Cum vag. j^^^/' = .00075". 



Sab. — In aquis quietis, Cumberland County, New Jersey. 



S. immersed, intermixed with other algae and adhering to aquatic plants ; filaments elongate ; 

 branches mostly geminate, more or less distant, short or elongate ; internal filaments bright 

 seruginous, sometimes distinctly articulate, at others not so, apex obtusely rounded aeruginous ; 

 joints about equal to the diameter or shorter; sheath ample hyaline, colorless; heterocysts 

 distinct, single, interjected, subcylindrical, sometimes about half as long as broad, sometimes 

 nearly twice as long. 



Remarks. — I found this plant in September, 1869, in Shepherd's Mill Pond, near 

 Greenwich, Cumberland County, New Jersey, forming, with other algae, a floccu- 

 lent, greenish-black, slimy coating to the stems and finely dissected leaves of 

 Bariunculus aquatilis. The branches are very few in number in most specimens, 

 and when they are more plentiful are apt to be short and abortive. Their apices 

 do not differ materially from their other portions. 



Fig. 9, pi. 2 a, represents a portion of a filament of this specimen magnified 750 

 diameters ; fig. 2 6a whole filament magnified 260 diameters. 



S. nraegelii, Ktz. (?) 



S. csesptoso-floccosum, bryophilum, nigro-viride; trichomatibus, plerumque sparse pseudora- 

 mosis, pseudoramulisque elongatis et intvicatis ; trichomatibus internis breviter articulatis, saspe 

 interruptis, saepe nonnihil moniliformibus, vlridibus aut in aetate provecta brunneis; articulis 

 saepe sejunctis, diametro plerumque brevioribus, subtiliter granulatis ; pseudoramulis plerumque 

 singulis ; vaginis modice arctis, interdum subamplis, baud distincte lamellosis, modice crassis, 

 hyalinis, coloris expertibus aut in aetate provecta dilute fusco-brunneis; cellulis perduranti- 

 bus nonnihil reniformibus, plerumque nullis, basilaribus. 



Diam. — Fil. cum vag. plerumque 7-/^^' — "'^'f- ^Aff" ! ^'ii® ^^E- t^^tttt"; cell, perdurant. lab. 



Syn. — S.Naegelii (Ktz.), Rabenhorst, Flora Europ. Algarum, Sect. II. p. 252. 



Hah. — In fonte, prope Belvidere, Centre County, Pennsylvania. 



Growing in small, blackish-green woolly mats attached to mosses ; filaments mostly sparsely 

 branched, with the branches elongate and intricate ; internal filament shortly articulate, 

 often somewhat moniliform, often interrupted, green, or, in mature state, brownish ; joints 

 often disjoined, mostly shorter than the diameter, finely granulate; branches mostly single; 

 sheaths moderately close, sometimes ample, not distinctly lamellate, rather thick, hyaline, 

 colorless, or, in old age, light fuscous brown ; heterocysts mostly wanting. 



Remarhs. — I found this plant in the large spring that supplies Bellefonte with 

 water, growing attached to mosses, so as to form little dark-green mats around 



