410 BULLETIN OF THE BUREAU OF FISHERIES. 
inous, so that they adhere together very easily... Propagation occurs by hormogonia— 
longer or shorter fragments of trichomes, breaking out the sheaths and moving of them- 
selves by circumnutation in the water, then, the movement ceasing, sheaths are formed 
and cell division commences. In the genera without sheaths—e. g., Oscillatoria, Spiru- 
lina—the movements persist throughout their life. 
The Oscillatoriacee inhabit principally moist, aerated places; many live in water 
containing decaying organic matter; some are incrusted with calcium carbonate; some 
thrive in temperatures as high as 85°C. 
About 550 species throughout the world. 
The members of this family are usually easily distinguished in that they do not taper 
to long hairs at the apices, they lack heterocysts, and in the majority of cases are un- 
branched. ‘The only species found in this region that is likely to be wrongly identified as 
belonging to this family is Plectonema battersii, one of the Scytonemaceze. ‘This species 
lacks hairlike apices and heterocysts and might easily be taken for one of the branching 
Oscillatoriacee. From these it can be easily distinguished by the fact that it has only 
one trichome within a sheath, while both Hy drocoleum and Microcoleus have several or 
many trichomes within each sheath. 
KEY TO GENERA. 
@., Sheaths absentt..:0. IWATA f VTL, PERO ROMTEN OTH 5c Fat eewial. ethedle slated sete - db. 
b. Trichomes straight or nearly so, multicellular .......... 22-222... eee eee eee 1. Oscillatoria (p. 410). 
bb. Trichomes forming a regular spiral, unicellular. .......-............... .2. Spirulina (p. 411). 
GOs SACALH PCS Ee Lee eke ee Ne eae ETE cette ee ne rie nate oR ewwits oi Aepe mar etere yeti aaron Eee c. 
c. Filaments consisting of one trichome within each sheath, simple............ 2 OAR a. 
d. Sheaths swollen, gelatinous, filaments more or less agglutinated ........ 3. Ptiscenidjres (p. 411). 
dd. Sheaths not swollen, firm, filaments free or forming a tangled mat, not agglutinated 
BE SD SOLE CORO OOS fon OTe: SATE On Se eR Aa ie Al omen ete 4 Aine ie 4. Lyngbya (p. 411). 
cc. Filaments consisting of several trichomes within a single sheath, simple or branched............¢. 
e. Filaments consisting of few trichomes within a single sheath, trichomes often loosely 
apprepatedi ss 25 EL. Jak Pokies Seto sict et erties es spe PO ERTIES RTE 5. Hydrocoleum (p. 413). 
ee. Filaments consisting of numerous trichomes within a single sheath, trichomes 
densely aggregated, often twisted into ropelike bundles.......... 6. Microcoleus (p. 413). 
Genus 1. Oscillatoria Vaucher, ex Gomont. 
Oscillatoria, Vaucher, 1803, p. 165. 
Oscillaria, Farlow, 1882, p. 32. 
Oscillatoria, Gomont, 1892, tome 16, p. 198. 
Trichomes cylindrical, free, usually motile, without a sheath or rarely inclosed in a 
very thin, fragile, mucous sheath, sometimes constricted at the joints, not moniliform, 
often attenuated at the apices, straight or curved or more or less regularly corkscrew- 
shaped in some species, but not constantly spiral; outer wall of apical cell thickened in 
some species, forming a calyptra. 
About 100 species in fresh or salt water, sometimes in hot springs or on moist earth, 
throughout the world. 
Oscillatoria nigro-viridis Thwaites, ex Gomont. 
Oscillatoria nigro-viridis, Thwaites, in Harvey, 1851, pl. 251a. 
Oscillaria limosa var. chalybea, Farlow, 1882 p. 33. 
Oscillatoria nigro-viridis, Gomont, 1892, tome 16, p. 217, pl. 6, f. 20. 
Oscillatoria nigro-viridis, Forti, in De Toni, 1907, p. 161. 
Oscillatoria nigro-viridis, Tilden, 1910, p. 69. 
P. B.-A. No. 1056. 
