OSCILLATOR lA. 



[ 560 ] 



OSCILLATORL\. 



trees and stones, never on the eaitli. Bri- 

 tish species miinerous, 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 eig-ht. Calyptra mostly covered 

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



B[BL. ^\'ilson, Bri/ol. Br. 185 ; Hooker, 

 Br. Fl. ii. pt. 1. 57 ; Vejitiiri, 31. M. Jn. 

 1881,80. 



OSCILLATO'RIA, Yaiich.— A genus of 

 OsL-illatoriacefe (Confervoid Alga?), distin- 

 giiislied from the allied forms by the simple, 

 rigid, elastic hlaments, 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 (PI. 8. fig. 8). 

 The young filaments or growing extremities 

 are continuous and scarcely striated ; but 

 by degrees transverse strife 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 strife after the action of thick 

 syrup (by endosmose) and after desiccation. 

 The curious rounding-off" of the separated 

 ends of dividing filaments (PI. 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 ■wiU be described 

 under Oscillatoriaceje. The filaments 

 ultimately break up at the strife into di- 

 stinct joints, -which may be regarded as 

 gonklia. 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. 



In fresh -vvater, or on damp earth, &c. 

 a. Stratum eeruginous or blue-green. 



O. limosa, Ag. Stratum dtirk green, 

 glossy, ■svith long rays; filaments green, 

 1-3300 to 1-3000" 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 fluating. 



O. muscorum, Ag. Stratum dark ;erugi- 

 nous-greeu, 3 or 4" in extent, growi)ig over 

 mosses in rapid streams ; filaments thickish, 

 pale blue-green. 



- O. tiafom, Oarm. Stratum ptile verdi- 

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

 resting on an ochraceous substratum ; fila- 

 ments hyaline, very slender. On fli.ating 

 sods in turf-pits. 



O. (h'corf leans, Grev. Stratum smooth, 

 glaucous-green, membranous, peeling off" in 

 fiakes ; filaments pale bluish green, very 

 slender. Damp w'alls, pumps, &c. ; common. 



b. Stratum dull green, inclining to purple, 

 black, or brown. 



O. nigra, Vauch. Stratum blackish 

 green (bluish black when dry), with long 

 radii; filaments pale bluish green, 1-2S00 

 to 1-3000" in diameter ; joints equalling or 

 a little shorter than the diameter. Ditches 

 and ponds. Common. 



O. autumnalis, Ag. (PI. 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, iSrc. Common. 



O. contexta, Carm. Stratum glossy black, 

 spreading three feet or more, appearing 

 satiny and striated to the naked eye; fila- 

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

 ticulations largish. On mud ; apparently 

 common. 



O. ochraeca^ Grev., is probably the same 

 as Leptothrix ochracea. 



** Marine, or in brackish witter. 



0. littoralis, Carm. Stratum bi-ight an'u- 

 ginous-green ; filaments deep green,' thicker 

 than in O. nigra ; joints one third the 

 diameter. Pools on the sea-shore. See 

 Symploca. 



BiBL. Harvev, Br. Alg. 1st ed. 161; 

 Mar. Alg. 228 ; 'Phgc. Brit. pis. 105, 251 ; 



