OSCILLATORIACE^. 103 



Strata varying in extent, lying on the surface of mud, or floating, or entangled with 

 other Algae and attached to them, of a very dull, blackish, or somewhat violet colour, 

 with shades of a;ruginous green. Filaments scarcely more than half the diameter of 

 those oi L. ferruginea ; with thin, membranous cell-walls, and densely annulated, dark 

 or duU coloured endochrome. When dry the stratum becomes brittle, and frequently 

 breaks off from the paper in flakes. 



Plate XLVII. D. Fig. 1. Lyngbya nigrescens, the natural size. Fig. 2. Portion of 

 a filament, magnified. Fig. 3. Section of the same, more highly magnified. 



5. Lyngbya confervoides, Ag. ; filaments very slender, flaccid, elongate, forming long, 

 comose fasciculi, floating freely from a blackish green basal stratum ; annuli not very 

 strongly marked. Ag. Syst. p. 73. Kiitz. Sp. Alg. p. 285. (Tab. XLVII. C.) 



Hab. Sea-shores, Charleston, S. Q;2t.vo\mSi,, Professor Lewis R. Gibbes. (v. s.) 



Stratum dark, olivaceous, or blackish green, emitting long bundles of slender filaments, 

 1-2 inches long, which float freely in the water. Filaments lying parallel in the 

 bundles, flexuous, but scarcely interwoven and often separate ; with very thin, narrow, 

 membranous tubes, and a dense, dull-green endochrome, which is much less distinctly 

 annulated than in L. ferruginea. The diameter of the filament is also much less than 

 in that species. 



I have compared the above quoted species with an authentic one from Professor 

 J. Agardh, and find little difference between them. 



Plate. XLVII. C. Fig. 1. Lyngbya confervoides, the natural size. Fig. 2. Portion 

 of two filaments, magnified. Fig. 3. Section, more highly magnified. 



6. Lyngbya pusilla, Harv. ; stratum minute, blackish-green ; filaments very slender, 

 short, crisped, spreading in small bundles ; endochrome pale, dull-green, annulate, cell- 

 wall very thin. (Tab. XLVII. E.) 



Hab. Parasitic on small Algae, at Sullivan's Island, S.C, W. H. H. (v. v.) 



This spreads over small Algae in thin strata, composed of densely matted filaments, 

 and emitting to all sides free, fascicled filaments. These latter are about quarter of an 

 inch long, and half the diameter of those of L. ferruginea^ with a pale endochrome. The 

 cell-wall is extremely thin ; the endochrome quite fills the tube, leaving a scarcely per- 

 ceptible margin. The annuli are tolerably definite. 



Possibly this may be an Oscillatoria. 



Plate XLVII. E. Fig. 1. Lyngbya pusilla., the natural size. Fig 2. Portions of 

 three filaments, magnified. Fig. 3. Section of a filament, highly magnified. 



