FRESH-WATBJR ALGiE OF THE UNITED STATES. 69 



blackish-green layer, which it makes upon the bark is very peculiar, being almost 

 membranaceous, and especially in the dried state, presenting a rough, somewhat 

 warty surface. The trichomata have the sheath more distinctly in the form of a 

 hollow cylinder, or, in other words, more plainly a sheath, than any other species 

 T have seen of the genus ; the cells are also without any apparent walls, and are 

 placed very closely together, so that the whole filament looks very like a scyto- 

 nema. 



Fig. 1, pi. 9, represents a portion of a frond magnified 260 diameters. 



S. pellncidnlus, Wood. 



S. immersus ; trichoraatibus ramossissimis, solitariis vel subsolitariis ; ramis plerumque unilar 

 teralibus, ramulosis; ramulorum apicibus late rotundatis, baud attenuatis; cellulis in serie- 

 bus simplicibus dispositis, in trichomatibus nonnihil rotundatis, in ramulis saepe angularibus, 

 plerumque corapressis, diametro sequalibus — 4 plo brevioribus ; terminalibus eylindricis et 

 obscure artieulatis ; cellulis interstitialibus nullis ; vaginis arctis, hyalinis, baud lamellosis ; 

 cytioplasmate asrugineo vel brunneo, minute granulato. 



Z»ia!m.— Trich. cum vag. 7/,/ = .00106" ; sine vag. = .0008". 



Syn. — S. pellucidulus, Wood, Prodromus, Proc. Amer. Philos. Soc, 1869, p. 133. 



Sab. — In stagnis, prope Hibernia, Florida. (M. W. Canby.) 



S. immersed ; filaments very much branched, solitary or subsolitary ; branches mostly unilateral, 

 branched ; apices of the branches not attenuate, broadly rounded ; cells disposed in a simple 

 series, in the trichoma somewhat rounded, in the branches frequently angular, mostly com- 

 pressed, from equal to 4 times shorter than the diameter ; terminal cell cylindrical, obscurely 

 articulate; interstitial cells none ; sheath close, hyaline, not lamellate; cytioplasm serugin- 

 ous or "brown, minutely granulate. 



Bemarhs. — This species was collected by Mr. William Canby in a little marsh 

 pool near Hibernia, Florida. The branches are given off in abundance, mostly in 

 a unilateral manner, are often very long, and about equal in diameter to the main 

 filament, and give origin to numerous branchlets. The sheaths are very trans- 

 parent and very close. I have never seen them in any way lamellate or fibrous, 

 or of any color. The cells do not have very apparent walls. In the main fila- 

 ment and branches they are globose, or, more commonly, very much compressed, 

 but in the newer branches, and sometimes in the older, they are very angular. 

 The few cells near the end of the branches are so shaped as to remind one of the 

 phalanges of the fingers. The last cell is cylindrical and has a number of cells 

 indicated in it. The color of the young cells varies from a deep bluish-green 

 to a ferruginous-brown — that of the older from a light bluish-green to ferruginous- 

 brown. 



Fig. 2 a, and 2 5, pi. 8, represent portions of filaments of this species. 



S. compactus, (Ag.) Ktz. 



S. strato expanso, tomentoso, fusco-nigro ; trichomatibus elongatis ramulisque adscendentibus, 

 apice interdura pauUum attenuatis sed ssepe clavatis, obtusis ; trichomatibus internis e cellu- 

 larum serie simplici formatis, et plerumque raoniliformibus ; cellulis diametro subsqualibus 

 vel brevioribus, subglobosis vel subquadratis, ssepe compressis ; cytioplasmate dilute caeruleo- 

 viride, subtiliter granulatis ; cellulis apicalibus eylindricis et oscillariura modo, siEpe indistincte. 



