LYNGBYA. 299 



plants colorless and thin ; older plants thicker, yellowish or 

 yellow brown, and lamellate. 



Diameter of filaments, 12-18 j*. 



Appears closely related to the submarine forms of L. aeru- 

 ginosa, Ag., L. pannosa, Kg 1 ., and L. aesfnarii, Liebm., but 

 beside electing fresh-water, it is thinner. According to 

 Kirchner the sheath is often very much wider than lias 

 come under my notice. L. bieolor, Wood, is the same plant. 



Plate CGI, figs. 5-10, from specimens from Bean Lake, 

 Canada ; ponds, Vermont ; Pennsylvania ; New Jersey ; 

 Alabama, and Florida. 



LYNGBYA PHORMIDIUM, Kg. 



Filaments much interwoven, forming mats of considerable 

 size, of dirty aeruginous color ; articulations nearly as long 

 as wide, light aeruginous, or turning yellowish brown. 

 Sheaths colorless, moderate in thickness, not lamellate. 



Diameter of filaments, 7-9.5 yw. 



Syn. Phormidium Lyngbyaceum, Kg.; Symploca phormidium, 

 Thur. 

 On wet marsh bottoms. 



Plate CCI, figs. 22-26, filaments somewhat variable in 

 thickness. 



Yar. EIVULARIS, Wolle. 



Filaments in larger or smaller tufts, from 1-6 inches long. 

 Attached to river stones in shallow, flowing water, waving 

 with the currents. Filaments often six inches long, the ex- 

 tremities bright blue-green, lower parts changing to yellow- 

 brown or fading entirely, becoming colorless. Articulations 

 usually indistinct, sub-equal in length and width. 



Diameter of trichomes, including the narrow sheath, 8-9 yw. 

 River Lehigh, Bethlehem, Pa. 



LYNGBYA ARENARIUM, (Kg.) Eab. 



Forming a thin membranaceous stratum, beautiful green, 

 not lamellose, trichomes lightly curved, pale aeruginous. 

 Articulations 3-4 to diameter. Apices of filaments obtuse 

 conical, straight. Sheaths often soft, gelatinous. 



Diameter of filaments, 8-10 yw. 



Moist low grounds near Atlantic Coast. 



Plate CCI, figs. 27-29, specimens from New Jersey, near 

 Atlantic City. 



