OSCILLATORIACE^. [ 562 ] OSCILLATORTACEvE. 



quires its double-spiral character from the 

 eutwining of origiually distinct filameuts. 

 Leptothriv and the allied genera are very 

 imperfectly known, and are only included 

 here from the absence of indications of closer 

 affinities elsewhere ; very likely thej'- are 

 mycelial filameuts of Fungi. 



These plants occur on damp ground, 

 rocks, or stones, and among Mosses and 

 other Confervse on rocks, stones, &c. in 

 fresh and salt water, and are allied in some 

 respects to the Nostochaceje ; but the 

 articulations of the filaments of the latter 

 are aU perfect cells with a complete cellulose 

 wall, multiplying by di-vision in the same 

 way as the Confervaceae. 



8yno2)sis of British Genera. 



A. Oscillatoriece. Filaments transversely 

 striated or moniliforai, sometimes spi- 

 rally curled ; sheathed, or, in the minute 

 forms, without evident sheaths; exhi- 

 biting spontaneous oscillating or creep- 

 ing motion. Increased by transverse 

 division. 



Didymolielix (PL 1. fig. 10). Filaments 

 brown, very slender, continuous, curled spi- 

 rally and twisted together in pairs. No 

 evident sheaths, but a common investing 



•ielly- 



Oscillatoria (PI. 8. fig. 8). Filaments 

 coloured, continuous, transversely striated, 

 readily breaking across, with a proper cellu- 

 lose sheath, oscillating ; collected in strata 

 and imbedded in a common gelatinous 

 matrix. 



Microcoleus (PI. 8. fig. 9). Filaments as 

 in Oscillatoria, but collected into bundles 

 in a common gelatinous dichotomously 

 branched tubular sheath ; filaments oscil- 

 lating. 



Cmnocoleus. Filaments branched, annu- 

 lated, contained with their ramifications 

 within a tough, more or less permanent 

 sheath which bursts irregularly. 



Symploca. Filaments as in Oscillaloria, 

 but erect and tufted, coherent at their bases, 

 bristling above. 



B. Lymibi/ea. Filaments motionless (r), 

 oscillarioid, enclosed in a very distinct 

 sheath, tufted, or forming strata, with 

 or witliout an enveloping jelly. 



Dasyylcea (PI. 8. fig. 11). Filaments un- 

 branched, sheathed; older sheaths broad, 

 coalescent outside into an amorphous gela- 

 tinous stratum. 



Lynyhya (PL 8. fig. 10). Filaments elon- 

 gated, distinctly articulated, unbranched, 

 with distinct convoluted cellulose tube, but 

 without a gelatinous matrix (motion creep- 

 ing ?) ; articulations very close. 



Liehleinia. Filaments short, erect, tufted, 

 unbranched, with distinct cellulose coat, 

 free, without an investing jelly. 



Chamcesiphon, Crenothrix, 



C. Scytonemece. Filaments distinctly arti- 

 culated, simple or branched, motionless, 

 with distinct articulations and large in- 

 terstitial (propagative ?) cells ; sheaths 

 at length softened and swollen, but with- 

 out a common gelatinous matrix. 



Scytonema (PL 8. fig. 19). Filaments 

 csespitose, or more rarely fasciculate, with 

 a double (lamellar) gelatinous sheath, 

 (mostly) closed at the apex ; branches con- 

 tinuoiis by lateral growing out of the pri- 

 mary filaments, with a knee-like base. 



Desmonema. Filameuts branched, more 

 or less coherent ; branches of two kinds, pri- 

 mary branches each with a connecting cell 

 at the base, secondary branches without 

 connecting cells; annulated. See Toly- 



POTHRIX. 



Arthronema (PL 8. fig. 20). Filaments 

 distinctly articulated, simple, in short 

 lengths, overlapping at their ends within 

 the gelatinous sheath. 



Petalonema (PL 8. fig. 21). Filameuts 

 branched, with the outer sheaths of the 

 single joints expanded upwards and out- 

 wards into fumiel-shaped bodies, each partly 

 overlapping its successor, forming a common 

 obhquely laniellated and transversely barred 

 gelatinous cyhnder. 



Calothrix (PL 8. fig. 22 ). Filaments very 

 closely articulated, tufted, with branches in 

 apposition for some distance, here and there 

 cohering laterally. Sheaths firm, often 

 darli-coloured. 



Tolypothrix, Filaments free, radiantly 

 or fastigiately branched, most distinctly 

 articulated at the bases of the branches ; 

 branches continuously excurrent, not in ap- 

 position ; sheaths thin, hyaline. 



Sirosip/toH. Filameuts single, double or 

 triple, within a distinct common sheath, 

 very distinctly articulated; branched by 

 lateral budding, the branches divergent. 



Schizothrix (PL 8. fig. 17). PMament.^ 

 branched by division ; sheaths laniellated, 

 thick, rigid, curled, thickened below, finally 

 longitudinally divided. 



Syinphyosiphon. Filaments erect or as- 



