OSCILLATORIA. 



trees and stones, never on the earth. Bri- 

 tish species numerous, remarkable for the 

 apophyses, sometimes having stomata, and 

 the varied character of the outer peristome, 

 the thirty-two teeth of which are variously 

 conjoined, so as to appear thirty-two, six- 

 teen, or eight. Calyptra mostly covered 

 with hair-like processes (fig. 472, p. 512). 



BIBL. Wilson, Bryol Br. 185 ; Hooker, 

 Br. Fl. ii. pt. 1. 57 j Venturi. M. M. Jn. 

 1881, 80. 



OSCTLLATO'RIA, Vauch. A genus of 

 Oscillatoriaceae (Confervoid Algae), distin- 

 guished from the allied forms by the simple, 

 rigid, elastic filaments, forming a stratum 

 in a common gelatinous matrix. Filaments 

 enclosed singly in tubular -cellulose sheaths, 

 open at the ends, from which the fragments 

 emerge when broken across (PL 8. fig. 8). 

 The young filaments or growing extremities 

 are continuous and scarcely striated ; but 

 by degrees transverse striae appear, some- 

 times very close together, sometimes dis- 

 tant, indicating a constriction and final 

 fission in the substance of the filament, 

 which, when old, readily breaks at these 

 places. The internal structure of the fila- 

 ment is obscure : it seems to be composed 

 wholly of protoplasmic substance, the joints 

 not possessing special cellulose coats; but 

 the substance of the filament, although 

 apparently solid, seems sometimes less dense 

 internally, since we have noticed a kind of 

 hour-glass contraction intermediate be- 

 tween the striae after the action of thick 

 syrup (by endosmose) and after desiccation. 

 The curious rounding-off of the separated 

 ends of dividing filaments (PL 8. fig. 8, 

 right-hand figures) seems to depend on some 

 power of expansion of an outer thicker layer 

 of the substance of the filament. The mo- 

 tion of the filaments will be described 

 under OSCILLATORIACE^J. The filaments 

 ultimately break up at the striae into di- 

 stinct joints, which may be regarded as 

 gonidia. No formation of spores has been 

 observed. A remarkable and unexplained 

 appearance is occasionally observed at the 

 growing ends of the filaments : they appear 

 crowned by a wreath of cilia ; but these 

 processes are rigid and motionless. 



The species occur on damp ground, on 

 stones, mud, in fresh water, running or 

 stagnant, in springs, and in brackish water ; 

 a few are truly marine. In the following 

 characters the colour of the strata is given 

 as seen by the naked eye, that of the fila- 

 ments as seen under the microscope. 



[ 560 ] OSCILLATORIA. 



* In fresh water, or on damp earth, &c. 

 a. Stratum ccruginotis or blue-green. 



O. limosa, Ag. Stratum dark green, 

 glossy, with long rays; filaments green, 

 1-3300 to 1-3600" in diameter; articulations 

 shorter than the diameter. At the bottom 

 of ditches and pools. 



O. tennis, Ag. Stratum dark green, thin, 

 with short rays ; filaments pale green, 

 1-4200" in diameter ; articulations equalling 

 or half the diameter. In muddy ditches, 

 &c. ; at first on the bottom, finally floating. 



O. muscorum, Ag. Stratum dark aerugi- 

 nous-green, 3 or 4' in extent, growing over 

 mosses in rapid streams ; filaments thickish, 

 pale blue-green. 



O. turfosa, Cann. Stratum pale verdi- 

 gris-green, glaucous, 1 or 1' in diameter, 

 resting on an ochraceous substratum ; fila- 

 ments hyaline, very slender. On floating 

 sods in turf-pits. 



O. decorticans, Grev. Stratum smooth, 

 glaucous-green, membranous, peeling off in 

 flakes ; filaments pale bluish green, very 

 slender. Damp walls, pumps, &c. ; common. 



b. Stratum dutt green, inclining to purple, 

 black, or brown. 



O. nigra, Vauch. Stratum blackish 

 green (bluish black when dry), with long 

 radii; filaments pale bluish green, 1-2800 

 to 1-3000" in diameter ; joints equalling or 

 a little shorter than the diameter. Ditches 

 and ponds. Common. 



O. autumnalis, Ag. (PL 8. fig. 8). Stra- 

 tum purplish or greenish black ; filaments 

 pale dirty bluish green, 1-4000 to 1-5000" in 

 diameter ; joints shorter than the diameter. 

 Damp ground, walls, &c. Common. 



O. contexta. Carm. Stratum glossy black, 

 spreading three feet or more, appearing 

 satiny and striated to the naked eye ; fila- 

 ments pate green, 1-3000" in diameter; ar- 

 ticulations largish. On mud ; apparently 

 common. 



O. ochracea, Grev., is probably the same 

 as Leptothrix ochracea. 



** Marine, or in brackish water. 



O. littoralis, Carm. Stratum bright aeru- 

 ginous-green ; filaments deep green, thicker 

 than in O. ni.gr a ; joints one third the 

 diameter. Pools on the sea-shore. See 

 SYMPLOCA. 



BIBL. Harvey, Br. Alg. 1st ed. 161; 

 Mar. Alg. 228; Phyc. Brit. pis. 105, 251 ; 



