64: FRESH-WATER ALG^E OF THE UNITED STATES. 



side to side, so that the interior is divided, as it were, into successive cell-like 

 chambers, in which the colored protoplasm is contained. This character seems 

 almost to separate the plant from the genus Scylonema, but I have deemed it 

 insufficient grounds for indicating a new genus. Since writing the preceding 

 remarks, I have received specimens of this species from Professor Ravenel, who 

 collected them in South Carolina, near the town of Aiken. They agree in all 

 respects, except that they form a dark, mucous, somewhat tomentose coating to 

 pieces of wood. 



Fig. 3 a represents the outline of a series of the cells alluded to, magnified 750 

 diameters, and figs. 3 b and 3 c, portions of filaments magnified 460 diameters. 



b. Arboricolse. 



b. Growing on trees. 



S. cortex, WOOD. 



S. minutissiraum, stratum tenue submembranaceum formante ; trichomatibus sparse pseudoramu- 

 losis, pseudoramulisque repentibus et plus minus concretis, viridibus aut dilute fuse-is, varie 

 curvatis, baud rigidis; cytioplasmate viride, articulate, rare distincte granuloso; articulis 

 diametro longioribus aut brevioribus; vaginis arctis, nonnihil tenuibus, plerurnque coloris 

 expertibus, sed. interdum dilute fuscis; cellulis perdurantibus et singulis et geminis, et basa- 

 libus et interjectis, globosis vel subglobosis. 



Diam. Trich. cum vag. 7S W TsW- 



Syn. Scylonema cortex, WOOD, Prodromus, Proc. Am. Philos. Soc., I860, p. 130. 



Sab. South Carolina. 



S. very minute, forming a thin, submembranaceous stratum ; filaments sparsely branched, toge- 

 ther 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 

 distinctly granulate; joints longer or shorter than broad; sheaths close, rather thin, trans- 

 parent, generally colorless but sometimes light brown ; heterocysts globular or subglobular, 

 single or in pairs, basal or otherwise. 



Remarks. I have specimens of this species collected in South Carolina by Pro- 

 fessor Ravenel, who found it growing on the bark of Platanus occidentalis. The 

 thin, almost membranous stratum which it forms, is of a dark olive-black, and has 

 to the eye a sort of minutely warty appearance. The filaments are so involved 

 and so adherent, one to the other, that I have not been able to separate any length 

 of them, nor are the branches distinguishable from the main filaments. The sheaths 

 are rather thin, and often not very apparent. 



Fig. 4, pi. 6, represents this species. 



S. Ravciiclii, WOOD. 



S. lignicola, breve csespitosum, viride-nigrum ; trichomatibus plerumque 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 ; tri- 

 chomatibus internis coloris expertibus, granulosis, saepe vagina erumpentibus, plerumque 

 articnlatis ; articnlis diametro longioribus aut brevioribus ; vaginis arctis, crassibus, fusco- 

 olivaceis vel anreo-fuscis, plerumque supra truncatis et apertis, superficie nonnunquam irregu- 

 laribus; cellulis perdurantibus subquadratis vel subglobosis singulis aut rare geminis, inter- 

 jectis ; in stato juvene trichomatibus internis rcrugineis, vaginis tenuibns. 



Diam. Trich. cum vag. TsV rft/i ram cum vag. 75 V 75 V; trich. sine vag. 

 2.0005." 



