OSCILLATORIACEiE. 



[ 477 ] 



OSCILLATORIACE^. 



longish-oval, with two to foiu' cross striae, 

 exhibiting a vibratory motion. No sheaths 

 evident. 



II. Vibrio (PI. 3. figs. 18-20). Filaments 

 extremely slender, moniliform, with an ac- 

 tive serpentine motion. No sheath evident. 



III. Spirulina (PL 3. figs. 15. 22. 23). 

 Filaments very slender, continuous or moni- 

 liform, curled into a long spiral or screw-like 

 form ; oscillating ; no sheaths evident, but 

 often a common investing jelly. 



. IV. DiDYMOHELix(Pl. l.fig. 10). Fila- 

 ments very slender, continuous, curled spi- 

 rally and twisted together in pairs. Motion?. 

 No evident sheaths, but a common investing 

 jelly. 



V. OsciLLATORiA (for this and the re- 

 maining genera see PI. 4). Filaments con- 

 tinuous, transversely striated, readily break- 

 ing across, Avith a proper cellulose sheath, 

 oscillating ; collected in strata and imbedded 

 in a common gelatinous matrix. 



VI. MiCROcoLEUs. Filaments as in 

 Oscillatoria, but collected in bundles in a 

 common gelatinous tubular sheath, which is 

 dichotomously branched; filaments oscil- 

 lating. 



VII. Symploca. Filaments as in Oscil- 

 latoria, but erect and tufted, coherent at 

 their bases, bristling above. 



B. LyriffbyecE. Filaments motionless(?), oscil- 

 larioid, enclosed in a very distinct sheath, 

 tufted, or forming strata, with or without 

 an enveloping jelly. 



VIII. Dasygl^a. Filaments unbranched, 

 sheathed ; older sheaths broad, coalescent 

 outside into an amorphous gelatinous stra- 

 tum. 



IX. Lyngbya. Filaments elongated, 

 distinctly articulated, unbranched, with di- 

 stinct convoluted cellulose tube, but without 

 a gelatinous matrix ; (motion creeping?) arti- 

 culations very close. 



X. Leibleinia. Filaments short, erect, 

 tufted, unbranched, with distinct cellulose 

 coat, free, without an investing jelly. 



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. 



XI. ScYTONEMA. Filaments csespitose, 

 or more rarely fasciculate, with a double 

 (lamellar) gelatinous sheath, (mostly) closed 



at the apex ; branches continuous by lateral 

 growing out of the primary filaments, w ith 

 a knee-like base. 



XII. Arthronema. Filaments distinctly 

 articulated, simple, in short lengths, over- 

 lajjping at their ends within the gelatinous 

 sheath. 



XIII. Petalonema. Filaments branched, 

 with the outer sheaths of the single joints 

 expanded upwards and outwards into fun- 

 nel-shaped bodies, each partly overlapping 

 its successor, forming a common obliquely 

 lamellated and transversely barred gelatinous 

 cylinder. 



XIV. Calothrix. Filaments very closely 

 articulated, tufted, with branches in apposi- 

 tion for some distance, here and there co- 

 hering laterally. Sheaths firm, often dark- 

 coloured. 



XV. ToLYPOTHRix. Filaments free, 

 radiantly or fastigiately branched, most di- 

 stinctly articulated at the bases of the 

 branches ; branches continuously excurrent, 

 not in apposition ; sheaths thin, hyaline. 



XVI. SiRosiPHON. Filaments single, 

 double or triple, within a distinct common 

 sheath, very distinctly articulated; branched 

 by lateral budding, the branches divergent. 



XVII. ScHizoTHRix. Filaments branched 

 by division ; sheaths lamellated, thick, rigid, 

 curled, thickened below, finally longitudinally 

 divided. 



XVIII. Symphyosiphon. Filaments 

 erect or ascending, enclosed in lamellated, 

 hard sheaths, concreted laterally at their 

 bases, involved in jelly. 



D. Rivulariece. Filaments distinctly arti- 

 culated, with an enlarged basal cell, 

 mostly attenuated above, connected into 

 definite or indefinite fronds ; motionless. 



XIX. ScHizosiPHON. Basal cells glo- 

 bose, filaments simple, distinctly articulated, 

 mostly attenuated towards the apex, sheathed, 

 sheaths connate into groups, hard, dark- 

 coloured, open and expanded above, and 

 overlapping so as to form a succession of 

 ochrese which have the free borders slit up 

 into filaments or fringes ; also displaying a 

 spiral-fibrous structure in dissolution. 



XX. Physactis. Filaments whip- 

 shaped, torulose at the base, sheathed, 

 sheaths simple, gelatinous ; collected into a 

 globose and solid, or subsequently a bullose- 

 vesicular frond; in the globose fronds the 

 filaments radiate from the centre; in the 

 vesicular fronds from the internal (lower) 

 surface of the gelatinous matrix. 



