388 THE MICROSCOPIST. 



a. Stratum ceruginous or blue-green. 



0. limosa. 0. tenius. 0. musconim. 0. turfosa. 0. 

 decor ticans. 



b. Stratum dull green inclining to purple, black, or 

 brown. 



0. nigra. 0. autumnalis. 0. cortexta. 0. ochracea. 

 * * Marine or in brackish water. 



0. littoralis. 



The above are species of Oscillatoria. 



A. OSCILLATORIE^:. Filaments transversely striate or 

 moniliform, sometimes spirally curled, sheathed, or in the 

 minute forms without evident sheaths. Spontaneous 

 oscillating, creeping, or serpentine motion. Increase by 

 transverse division. 



1. Bacterium. Filaments colorless, very small, short, 

 wand-shaped, or longish-oval, with two ' to four cross 

 striae, exhibiting vibratory motion. 



2. Vibrio. Filaments colorless, very slender, monili- 

 form. Active serpentine motion. 



3. Spirulina. Filaments green, very slender, continu- 

 ous or moniliform, curled into a long helical or screw 

 form ; oscillating. 



4. Didymohdix. Filaments brown, very slender, con- 

 tinuous, curled spirally and twisted in pairs. 



5. Oscillatoria. Filaments colored, continuous, trans- 

 versely striated, readily breaking across ; a proper cellu- 

 lar sheath ; oscillating ; in strata imbedded in gelatin. 



6. Microcoleus. Filaments as in 5, but in bundles in a 

 common gelatinous sheath, tubular and dichotomously 

 branched. Filaments oscillating. 



7. C&nocoleus. Filaments branched, contained in a 

 tough, more or less permanent sheath, which bursts ir- 

 regularly. Filaments annulated. 



8. Symploca. Filaments as in 5, but erect and tufted, 

 coherent at base, bristling above. 



