FRESn-WATER A L G .E OF THE UNITED STATES. 65 



Syn. — S. Bavenelii.Woos, Prodromus, Proc. Am. Philos. Soc, 1869, p. 130. 



Sab. — In cortice, South Carolina. 



S. Forming little turfy spots of a greenish color, on bark ; filaments mostly creeping, either 

 brownish-olive or yellowish-brown, moderately branched ; branches ascending, rigid, flexu- 

 ous, very rarely provided with secondary braachlets, either brownish-olive or yellowish- 

 brown, rarel}^ subtransparent at the apex; cytioplasm colorless, granular, often extending out 

 beyond the sheaths, generally articulate ; joints longer or shorter than broad ; sheaths close, 

 thick, brownish-olive or yellowish-brown, for the most part truncate at their ends and open, 

 their surface sometimes irregular ; heterocysts subquadrate, single, interstitial. 



Remarhs. — I am indebted to Prof. H. W. RaA'enel for specimens of this very 

 distinct species. Some of these are labelled as having grown on the twigs of a 

 ccltis in South Carolina, other specimens are on the bark of a willow. The branches, 

 which are mostly shortish, simple, and variously curved, are sent up in great 

 numbers by the creeping stems, and, like the stems themselves, are mostly free, 

 but not unfrequently are closely adherent by their edges. 



The internal trichoma or cytioplasm, owing to the great thickness of the sheaths, 

 is not very apparent within these latter, but not unfrequently projects for a dis- 

 tance beyond them, when it is seen to be colorless, very granular, and mostly, but 

 not always, distinctly articulated. In the young plant the filaments are bright- 

 green, often not more than ^gV o of an inch in thickness, and have the sheath very 

 thin, or may be almost imperceptible. It affords me great pleasure to dedicate 

 this species to Professor Ravenel, not as an acknowledgment merely of his aid in 

 my studies of this hitherto neglected branch of the North American Flora, but 

 rathe* of the great services he has rendered science in some of its kindred 

 branches. 



Fig. 4, pi. 5, represents the end of a filament of this species magnified some 450 

 diameters. 



Genus TOLYPOTHRIX, Ktz. 



Trichoma scytonemacea cum cellulis perdurantlbus seriatis. 



Filament similar to that of scytonema, but with the heterocysts seriate. 



T. distorta, (Mijller) Kotz. 



T. ciEspitoso-floccosa, Iste et pnlchre viridis ; trichomatibus intertextis, Isete viridibus, raodo 

 distincte articulatis niodo inarticulatis; articulis diametro brevioribus siepe aut sub-nullis 

 aut nullis ; pseudoramulis singulis; vaginis arctis, homogeneis, vltreis ; cellulis perdurantlbus 

 basilaribus et interdum interjectis, pachydermaticis, plerumque in parallelogramma; enormis 

 forma, plerumque 4-seriatis, subachrois, interdum sparsissime granulatis. 



Syn. — T. distorta, (MiJLLER) Ktz. Rabenhorst, Flora Europ., Algarum, Sect. II. p. 275. 



Eab. — In aquario, Philadelphia, Wood. Rhode Island (Olney) Thwaites. Warden's Pond, 

 Rhode Island ; Reservoir Pond, West Point ; Fourth Lake, Madison, Wisconsin, Bailey. 



Flocculent caespitose, bright, beautiful green ; filaments interwoven, bright green, partly dis- 

 tinctly articulate, partly continuous ; articles shorter than long, often very indistinct, some- 

 times absent; branches single; sheaths close, homogeneous, glas.«y ; heterocysts basilar, 



9 May, 1872. 



