298 FRESH-WATER ALG^ OF THE UNITED STATES. 



It does not strictly represent the plant of (Kg.) Bab., but 

 has so much in common, have adopted the name for it. 

 i It is near L. aestuarii, but separated by the thin and often 



gelatinous sheaths ; in the mixture of sizes of filaments, and 

 color of strata; not deep aeruginous; neither is it sub-mem- 

 branaceous, as that plant. 



The features may be largely characteristic of young devel- 

 opments from Anabce,na-\ils& filaments, as explained under 

 the description of the genus Anabcena. 



LYNGBYA PAIXIDA, (Naeg. ) Kg. 



Forming a firm niembranaceous stratum, pale rose or 

 darker red color. Trichonaes rather straight or slightly 

 curved, subparallel, or sometimes flexuously curved and in- 

 terwoven; in older condition faded, or yellowish brown. 

 The filaments at first bright aeruginous, but soon change ; 

 usually they occur intermixed in color; aeruginous, pink, 

 darker red, yellow, and almost colorless. Articulations 

 equal to half as long as wide. Sheaths ordinarily rather 

 wide, widen with age, finally lamellate and fibrillous. 



Diameter with sheath varying from 40-80 yu. 



Syn. Hypeoi/irix pallida, (Naeg.) Kg.; Phormidium pallidum, 

 Naeg. 



Exposed wet soil, old roadways, old meadow grounds, 

 New Jersey, Virginia, Florida, Pennsylvania. 



Plate CCII, figs. 26-31, various stages of growth. 



LYNGBYA NAVEANUM, GTUII. 



Occurs in thin strata, dull green, or olivaceous brown. 

 Trichomes dull aeruginous ; articulations often indistinct, 

 i-i as long as wide. Sheaths close, but widen with age; 

 firm, colorless. Filaments more or less parallel, internal 

 trichomes frequently interrupted. 



Diameter of filaments, with sheath, 15-18 yw. 



Marsh grounds, Florida; Crystal Bay, Canada; pools, 

 Pennsylvania. 



Plate CCI, figs. 1, 2, from Pennsylvania specimens ; figs. 

 3, 4, Florida specimens. 



LYNGBYA OBSCURA. 



Free swimming in solitary filaments, but frequently form- 

 ing a thin dark aeruginous, almost black, stratum. Articu- 

 lations distinct, i-i as long as wide ; primarily bright aeru- 

 ginous, later some shade of brown. Sheath in younger 



