376 ALG^S CONFERVOIDEiE. [Oscillator in. 



In pools, along the muddy sea-shore, flooded by spring-tides. Appin, 

 Copt. CarmichaeL — '? Stratum exceedingly thin, slimy, bullated by the 

 extrication of air-bubbles, of a dark-green colour, spreading to an inde- 

 finite extent over the muddy bottom of the pool. Filaments 1 — 2 lines 

 in length, much thicker than those of O. nigra, straight or slightly 

 curved, radiating very irregularly and generally in twisted bundles. 

 Stria? strongly marked, at intervals of about one-third the diameter of 

 the filament." Carm. MSS. — Mostly allied to O. limosa. In a dry 

 state, it is membranaceous, and scarcely adheres to paper. 



14. O. subsdlsa, Ag. ? (submarine Oscillatoria); stratum 

 membranaceous seruginose-green smooth, filaments slender 

 densely interwoven, strise distant indistinct. — Ag. Syst. Alg. 

 p. 66? 



At Brighton, " on a plank, between high and low-water mark," Mr. 

 Borrer. — Stratum aeruginose or bluish-green, smooth, without gloss, 

 when dry, peeling off in membranaceous flakes ; filaments hyaline, slen- 

 der, densely packed, either straight or curved; strice not very evident. 

 In habit, it somewhat resembles O. lit t oralis ; but the filaments are much 

 slenderer, and the stratum more membranaceous. 



*** Nigrescentes. Stratum of a dull indistinct green, or inclin- 

 ing to purple, black or brown. 



15. O. nigra, Vauch. (blackish Oscillatoria); stratum black- 

 ish-green (when dry bluish-black) with long radii, filaments 

 pale bluish-green thick, strise very distinct and close. — Hook. 

 Scot. P. II. p. 79. Ag. Syst. Alg. p. 63. — Conferva fontina- 

 lis, Dilliv. Conf. t. 64. — O. limosa, Grev. Fl. Edin. p. 303, 

 (not of Ag.) 



Ditches and ponds, common. — Stratum extensive, blackish with a 

 shade of green, when dry blue-black, very rapid in its growth and send- 

 ing out long, vividly oscillating rays. Dillwyn's figure of Confervafon- 

 tinalis answers this species pretty correctly; but his description seems to 

 take in many others. 



16. O. autumndlis, Ag. (autumnal Wall Oscillatoria'); stratum 

 purplish or greenish-black very lubricous shortly radiating, fila- 

 ments pale bluish-green, strise subdistant — Ag. Syst. Alg. p. 62. 

 Lyngb. Hydroph. Dan. p. 95. Grev. Fl. Edin. p. 305. 



On damp walls, abundant in autumn and winter. — Stratum extensively 

 spreading, very dark and lubricous, glossy when dry; fdaments remark- 

 ably pale ; striae not very evident. 



17. O. contexta, Carm. (satin-like Oscillatoria); stratum 

 glossy black strongly striated, filaments thickish pale-green, 

 strise subdistant. 



On moist ground; Appin, Capt. CarmichaeL—" Stratum of indefinite 

 extent, three feet and upwards, exceedingly thin and peeling off in large 

 flakes in dry weather, of a deep but shining black colour, scored or 

 striated in all directions. These striae are caused by thick fasciculi of 

 filaments, shooting out either parallel to or across each other, changing 

 their course from time to time, and sending off lateral fasciculi. The 



