312 FRESH-WATER ALG^E OF THE UNITED STATES. 



lating, articulations as long or half as long as the breadth ; 

 dissepiments finely granulate ; apices obtuse or slightly at- 

 tenuate ; cell contents bright aeruginous. 



Diameter of filaments, 4-5 //. 



Plate CCVI, fig. 9, not infrequent in stagnant or sluggish 

 waters. 



OSCILLARIA CRUENTA, Gl'Un. 



Filaments light aeruginous imbedded in gelatinous masses 

 which are hyaline or somewhat tinted with green or purple. 

 Filaments primarily closely coiled, but soon unroll, remain- 

 ing somewhat tortuous. Articulations often indistinct; 

 after division about one-half longer than broad. 



Diameter of trichomes, 5 yw, a little more or less. 



Plate CCVII, figs. 1-3, parts of ordinary trichomes ; figs. 

 4-7, young coiled trichomes. 



Plate CCVI, fig. 5, parts of filament of a gathering of a 

 previous season, varying from 4-6 jn. 



Unlike usual forms of Oscillaria, this was gathered sev- 

 eral successive years (1882 1885) imbedded in large sub- 

 merged, almost hyaline, firm, gelatinous masses of irregular 

 form, averaging about the size of a man's head. These oc- 

 curred in a mountain spring at about 1500 feet elevation. 

 Beside the filaments, there are scattered through the masses 

 spherical cells by twos and by fours, constituting them 

 Tetraspora gelatinosa, Desv. An effort to identify a rela- 

 tionship between the filaments and the Tetraspora cells was 

 not successful, although there is a striking similarity in the 

 purplish tint of the two. 



OSCILLARIA SUBFUSCA, Vauch. 



Forming a somewhat dense stratum, dark olive or nearly 

 black, short rayed. Filaments nearly straight, with ends 

 sometimes attenuated and furnished with two short cilia. 

 Articulations, *- 1 times as long as wide. Cell contents light 

 aeruginous. 



Diameter of filaments, 4.6-6.6 //. 



Plate CCVI, figs. 11-13, several varieties of filaments. 



OSCILLARIA BREVIS, Kg. 



Forms a thin, aeruginous stratum, filaments longer or 

 shorter, somewhat attenuated near the ends, and slightly 



