io8 Minnesota Algae 



merged. Conanicut Island. August 1894. (Richards). New Jersey. On 

 moist soil. (Wolle). Pennsylvania. On damp earth. (Wolle). Minne- 

 sota. Gull Lake. July 1893; on sides of stone basin over-flowed by spring 

 water, between New Duluth and Fond du Lac, near Duluth, Aujgust 1901. 

 (Tilden). Iowa. Iowa City. (Hobby). Damp soil. Grinnell. (Fink). Ne- 

 braska. On damp soil in greenhouse; around pumps, cisterns, Lincoln. 

 (Saunders). Washington. Coupeville, Whidbey Island; La Conner, Skagit 

 County; Seattle, (Gardner). 



212. Phormidium setchellianum Gomont. Monogr. Oscill. 210. pi. 5. fig. 25, 

 26. 1893. De Toni. Syll. Algar. 5: 254. 1907. 



Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 2. no. 52. 1895. 

 Plate V. fig. 20, 21. 



Plant mass thin, cobwebby, dark purple, when dried dark lead-colored; 

 sheaths delicate, usually diffluent into an amorphous mucus; trichomes 

 4-4.8 mic. in diameter, parallel, straight or rCioderately flexuous, not con- 

 stricted at joints; apex of trichome scarcely tapering, curved or hooked, 

 capitate; apical cell showing a depressed-conical calyptra; cells 3-6 mic. in 

 length; transverse walls, often showing a double row of granules; cell con- 

 tents pale purple. 



Connecticut. Forming arachnoid expansions on stones at the bottom 01 

 a swift brook. In the living condition the expansions are of the color of 

 Bangia fusco -purpurea. Norwich. July 1890. (Setchell). 



Genus LYNGBYA C. Agardh. Syst. Algar. XXV. 1824. 



Filaments free, unbranched, free-floating or forming a densely intricate 

 floccose or expanded mass; sheaths firm, of variable thickness, sometimes 

 lamellose, colorless or rarely yellowish brown; trichomes sometimes con- 

 stricted at the joints, either obtuse or slightly tapering at the apices; outer 

 wall of apical cell sometimes thickened forming a calyptra. 



I Trichomes not more than 2 mic. in diameter. 



1 Plants living in salt water, epiphytic; transverse walls marked by 



two refringent granules 

 (i) Filaments i.S mic. in diameter; trichomes .5 mic. in diameter, 

 cylindrical, not constricted at joints; cells i.S mic. in length 



L. mucicola 

 (2) Filaments 1.5-2 mic. in diameter; sheaths very thin, scarcely vis- 

 ible; cells 2-7 mic. in length L. perelegans 



2 Plants living in fresh water 

 (i) Sheaths thin, colorless 



A Filaments coiled or spiraled 



a Filaments coiled; trichomes .8 mic. in diameter, constricted at 



joints; cells 2.3-3.2 mic. in length L. rivulariarum 



b Filaments more or less regularly spiraled, sometimes straight; 



trichomes 2 mic. in diameter; cells 1.2-3 mic. in length 



L. lagerheimii 



