OSCILLATORIA. 



[ 475 ] 



OSCILLATORIACE.E. 



been described under Oscillatoriace^. 

 The filaments ultimately break up at the 

 strife into distinct joints, which may be re- 

 garded as gonidia. No formation of spores 

 has been observed. A remarkable and un- 

 explained appearance is occasionally observed 

 at the growing ends of the filaments ; they 

 appear crowned by a wreath of cilia, but 

 these processes are rigid ; no motion of them 

 has ever been seen. 



Kiitziug has multiplied the species beyond 

 all reason, and sepai'ated some without good 

 grounds under the name of Phormidium. 

 \Ve follow Harvey in the enumeration of the 

 commoner British species; but this genus, 

 like its allies, requires a thorough study of 

 recent specimens. They occur on damp 

 ground, on stones, on mud, in fresh water, 

 running or stagnant in springs and in brack- 

 ish 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 filaments as seen under the microscope. 



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

 a. Stratum eeruginous or blue-green. 



1. 0. limosa, Ag. Stratum dark green, 

 glossy, ^ith long rays; filaments green, 

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

 shorter than the diameter. At the bottom 

 of ditches and pools. 



2. 0. tenuis, 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 to the top. 



3. O. muscorum, Ag. Stratum dark seru- 

 ginous-green, 3 or 4" in extent, growing over 

 mosses in rapid streams; filaments 'thickish,' 

 pale blue-green. 



4. O. turfosa, Carm. Stratum pale ver- 

 digris-green, glaucous, 1 or H' in diameter, 

 resting on an ochraceous substratum; fila- 

 ments hyaline, S'crj^ slender.' On floating 

 sods in turf-pits. 



5. O. decurticans, Grev. Stratum smooth, 

 glaucous-green, membranous, peeling off^ in 

 flakes ; filaments pale bluish - green, ' very 

 slender.' Damp walls, pumps, &c. ; com- 

 mon. 



b. Stratum dull green, inclining to imrple, 

 black, or brown. 



6. 0. nigra, Yauch. 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. 



7. 0. autumnalis, Ag. (PI. 4. 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. 

 Dam]) ground, walls, &c. Common. 



8. O. contexta, Carm. Stratum glossy 

 black, spreading three feet or more, appear- 

 ing satiny and striated to the naked eye; 

 filaments pale green, 1-3000" in diameter; 

 articulations largish. On mud ; apparently 

 common. 



O. ochracea, Grev. is probably the same 

 as Leptothrix ochracea. 



** Marine, or in brackish water. 



9. 0. littoralis, Carm. Stratum bright 

 aeruginous - green ; filaments deep green, 

 'thicker than in O. nigra;' joints one-third 

 the diameter. Pools on the sea-shore. 



Other species are described, but without 

 dimensions, so that they are obscm'e with- 

 out the aid of figures. See also Symploca. 



BiBL. Harvev, Brit. Alg. 1st ed. p. 161, 

 Br.Mar.Alg.\^.22S, Phyc.Brit. pis. 105,251; 

 Hassall, Br. Fr. Alg. p. 244. pi. 70-/2; 

 Kiitziug, Sj). Alg. p. 237, Tab. Phyc. Bd. i. 

 pis. 38-44. 



OSCILLATORIACEJE. — A family of 

 Coufervoid Algae, containing organisms of 

 considerable diversity and not very well cha- 

 racterized at present, owing to the obscurity 

 of the reproduction. The genus Oscillatoria, 

 with its nearest allies, is composed of cylin- 

 drical filaments of protoplasmic substance, 

 invested by a continuous cellulose sheath or 

 tubular cell-membrane. The internal (solid?) 

 filament gradually becomes transversely 

 striated as it increases in age, and subse- 

 quently readily breaks across at the trans- 

 verse lines, and the fragments readil}^ escape 

 from the sheaths, since no cross-walls of 

 cellulose are produced (PI. 4. fig. 8). These 

 kinds exhibit clearly the remarkable motion 

 from which the family takes its name. They 

 are mostly found upon damp ground, form- 

 ing wide and irregular strata; Rivularia and 

 the allied genera have the joints of the fila- 

 ments more distinct, and the filaments are 

 coherent into definite fronds, on which they 

 stand erect or radiate from a centre (PI. 4. 

 figs. 13. 16). The sheaths become compli- 

 cated in many of these, from the internal 

 multiplication and the persistence of the 

 cellulose sheaths of several generations one 

 within another (see Petalon EM a), often ge- 

 latinously swollen up and sometimes decom- 



