FRESH-WATER ALG^ OF THE UNITED STATES. 76 



Remarhs. — This species was found in winter by Prof. H. W. Ravenel in South 

 Carolina, growing upon the bark of Ilex Oi.aca, forming minute, firm, crustaceous, 

 roundish dots or masses, much smaller than a mustard-seed,' but in some cases so 

 closely aggregated as almost to make a continuous strattim. When one of these 

 dots is placed under the microscope, the branches are seen presenting their ends 

 upon all sides, reminding one of some varieties of coral, and between these are 

 blackish matters, which prevent the whole dot from being seen. These branches 

 are frequently placed very close to one another, and cohere by their edges so as to 

 make a sort of membrane or a solid mass. The filaments themselves are mostly 

 obscured in the dense mass of branches which clothe them. This species seems 

 to be closely allied to S. coralloides, and I am not certain whether it is distinct or 

 not. It is certainly very much smaller. 



S. pulvinatus, Br£b. 



S. pulvinatus, humectatns, saturate olivaceo-niger, ad tres lineas crassus; trichomatibus crassis- 

 simis, ramossissimis, fuscescentibns, enormiter curvatis ; ramulis polymorphis pro S3tate cras- 

 sitie magnitudineque variis, apice plerumque obtuse rotundatis ; trichomatum cellularura serie 

 multiplici, ramulorum 2-4 plici ; vaginis crassis, luteo-fuscis ad saturate-fuscis, vel pellucidis 

 vel non pellucidis, interdum rugoso-tuberculis. 



Diam. — Trich. cum. vag. max. .0042". 



Syn. — S. pulvinatus, (BafiB.) Rabenhorst, Flora Europ. Algar., Sect. II. p. 290.' 



Mob. — In rupibus prope Philadelphia. Wood. 



In moist, deep olive-black cushion-like masses of two or three lines thick ; filaments very thick, 

 much branched, brownish, irregularly curved ; branches polymorphous, varrying in thickness 

 and size, mostly with their apices obtuse ; cells of the filament many seriate, of the branches 

 two to four seriate; sheaths thick, yellowish-fuscous to deep fuscous, pellucid or opaque, 

 sometimes rugose-tuberculate. 



Remarks. — I have received specimens of this species found by Mr. Austin in 

 Northern New Jersey, growing on the exposed face of rocks. 



The size attained to exceeds that given by Mr. Rabenhorst for the European 

 form. The color of the cytioplasm varies from an almost verdigris-green to 

 fuscous. 



Besides these specimens. Dr. I. Gibbons Hunt has given me fresh ones of a 

 Sirosiphon which he found growing on the face of dripping rocks along the 

 Wissahickon Creek, near this city. These are much smaller in every way than 

 their more northern brethren, and diff"er in other respects, I think, sufficiently for 

 a distinct variety. The filaments and branches are much flatter than in Mr. 

 Austin's specimens. I append a description. 



( Yar. parTlls.) 

 S. trichomatibus in csespite saturate olivaceo-nigro arete intertextis; trichomatibus erassissimis, 



enormiter ramosissimis, luteo-fuscescentibos, varie curvatis.; ramulis polymorphis, apice 



plerumque obtuse rotundatis; trichomatum cellularum serie multiplici, ramulorum 1-4 plici ; 



cytioplasmate grannlato, plerumque saturate fuscescente, interdum Isete viride ; vaginis crassis, 



dilute luteo fuscescentibus, interdum achrois. 

 Diam. — Trichom. cum. vag. max. ^\-g" = .03" 



