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



contents light aeruginous, homogeneous or slightly granular. 

 Diameter of filaments, 6-7. 75 ^ ; more rarely 8-9 //. 



Syn. Conferva limosa, Roth ; Oscillaria Adansonii, Vauch. ; 

 0. tennis, var. limosa, Kirch. 



Babenhorst enumerates ten varieties, differing chiefly in 

 color; as laete aeruginosa, Kg.; rufa, Kg.; fuscescens, Bab.; 

 chali/bea, Kg.; subfmca, Kg.; amethysteo-chalybea, Kg.; 

 others in form and habitat, as luic'utata, Ag.; fontana, Kg.; 

 animalis, Kg.; and circulate, Bab. 



Plate CCVI, fig. 16, merely a few ends of trichomes of 

 which thousands are interlaced to compose a stratum as 

 usually observed on moist, muddy soils. 



OSCILLARIA NATANS, Kg. 



Filaments often interwoven into a bright aeruginous stra- 

 tum, but more frequently, (var. eryptarthra, Kg.,) solitary 

 and long, twining around water plants ; or free swimming 

 in ponds of quiet waters ; ends of filaments somewhat atten- 

 uated, apices obtuse. Articulations distinct, nearly as long- 

 as wide, more rarely only half as long. Sometimes slightly 

 contracted at the joints. Cell contents light aeruginous or 

 changing to olivaceous. 



Diameter of cells, 6.5-8.2 yu. 



Plate CCVI, fig. 19, parts of filaments, frequent in many 

 ponds of New Jersey. 



OSCILLARIA CHALYBEA, Mertens. 



Free swimming, long radiating ; stratum broadly ex- 

 panded, obscure blue-green or steel blue color. Filaments 

 pale steel blue, changing to olivaceous, lightly flexuous ; 

 articulations distinct i-l as long as wide ; ends of filaments 

 somewhat curved, apices usually obtuse, rarely rostellate. 

 Cell contents light steel blue ; granulate. 



Diameter of cells, 7-8 /*. 



Plate CCVI, figs. 17 and 21, fragments of filaments col- 

 lected from wet grounds, Florida. 



OSCILLARIA ANGUINA, Bory. 



Stratum thin, membranaceous, green or dark blue-black, 

 filaments thicker than the last, straight or curved ; cells 

 usually about half as long v as wide, slightly contracted at 

 the joints; contents light aeruginous; apices bluntly 

 rounded. 



Diameter of filaments, 9-11 //. 



