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



4. Var. ornata, Bab. Stratum dull steel blue ; diameter of 



filaments, 10 yw. 

 5. --Var. fusca, Kirch. Very dark olive brown, cell contents 



olive green, otherwise like first form. 



6. --Var. caerulea, Kg. Trichomes light -blue. 



7. --Var. violascens, Eab. Stratum dark steel blue, shining; 

 trichomes beautiful violet steel, articulations 2-4 

 to diameter. 



8. Var. neglecta. Wood. Near the latter. Filaments di- 

 lute purplish lead color, or leaden -gray. Stratum 

 blackish purple. 



Plate CCVII, figs. 9, 10, from forms most frequent. Com- 

 mon on sluggish waters, pools, and the like. 



OSCILLARIA MAJOR, Vauch. 



Stratum aeruginous or dark steel blue. Filaments thicker 

 than the preceding, straight, ends slightly attenuated ; cells 

 i-jj as long as wide, with ends bluntly rounded ; contents 

 steel blue. 



Diameter of filaments, 19-22 ^. 



Plate CCVII, figs. 11, 12, specimens from borders of 

 ponds and pools. 



OSCILLARIA GRATELOUPII, Bory. 



Stratum aeruginous, long radiating; trichomes nearly 

 straight, subfragile, unequal in diameter ; thicker filaments, 

 18-20 IJL. Articulations \-\ as long as wide ; dissepiments 

 ornate, with usually two series of granules. Ends of fila- 

 ments straight, broadly rounded. 



Only habitat hitherto observed, vicinity of New York 

 City, submarine waters. 



Plate CCVII, figs. 13-15, various sizes as they were found 

 intermingled. 



OSCILLARIA BONNEMAISONII, Crouau. 



Stratum more or less extended, dark aeruginous or oliva- 

 ceous ; filaments long radiating, dark aeruginous, flexuously 

 curved, interwoven ; articulations one-fourth to one-fifth as 

 long as wide, dissepiments distinctly granular, ends atten- 

 uated, curved, apex rounded. 



Diameter of filaments, 23-28 yu. 



Wet soil, recently inundated, Pennsylvania. 

 Plate CCVII, figs. 16, 17, two ends of motile filaments. 



