64 PRESH-WATER ALG^ OP 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 Seytonema, 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 Kavenel, 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 h and 3 c, portions of filaments magnified 460 diameters. 



h. Arboricolae. 



b. Growing on trees. 



S. cortex, Wood. 



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

 losis, pseudoramulisque repentibus et plus minus concretis, viridibns aut dilute fuscis, varie 

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

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

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

 libus et interjectis, globosis vel subglobosis. 



Dwm.— Trich. cum vag. ^/^"_^/^^". 



Syn. — Scytonema cortex, Wood, Prodromus, Proc. Am. Philos. See, 1869, 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 subglobnlar, 

 single or in pairs, basal or otherwise. 



Bemarhs. — 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. Barenelii, Wood. 



S. lignicola, breve CKspitosum, Viride-nigrum ; trichomatibus plerumque repentibus, vel fusco- 

 olivaceis vel aureo-fuscis, modice pseudoramosis ; ramis ascendentibus, rigidis, fle'xuosis rare 

 pseudoraraulosis, vel fusco-olivaceis vel aureo-fuscis, rarissime cum apicibus subachrois; tri- 

 chomatibus internis coloris expertibus, granulosis, sa;pe vagina erpmpentibus, plerumque 

 articulatis ; artieulis diametro longioribus aut brevioribus ; vaginis arctis, crassibus, fusco- 

 olivaceis vel aureo-fuscis, plerumque supra truucatis et apertis, superflcie nonnunquara'irregu- 

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

 jectis ; in stato juvene trichomatibus internis serugineis, vaginis tenuibus. ' j 



^'""^oTJ??' ""^ ''^^' ^^''^'^"-^^'^'^"' '""^ ^"""^ ^^S- t/ttV'-tsV; trich. sine vag. W^/' 



