286 Minnesota Algae 



Tilden. American Algae. Cent. I. no. 8i. 1894; List of Fresh-Water Al- 

 gae colkcted in Minnesota during 1894. Minn. Bot. Studies. 1: 236. 1896. 



Colonies spherical or somewhat oval, firm, solid, about the size of a 

 very small pea, crystal-bearing, light green; filaments straight or slightly 

 curved, produced into long hairs, not regularly articulated; apex of fila- 

 ment straight or slightly curved, mostly indistinctly articulate, frequently 

 interrupted; sheaths ample, transparent, saccate, sometimes strongly con- 

 stricted; lower cells in the mature filament short and generally compressed; 

 gonidia cylindrical, frequently curved, about nine times as long as broad. 



Pennsylvania. Growing attached to small water plants. Schuylkill River, 

 near Spring Mills, Philadelphia. (Wood). Minnesota. Attached to Chara. 

 1-ake Minnetonka, Hennepin County. August 1894. (MacDougal). 



521. Rivularia echinulata (Smith) Bornet and Flahault. Sur la Determina- 



tion des Rivulaires qui forment des Fleurs d'Eau. Bull. Soc. Bot. 



de France. 31: 76. 1884. De Toni. Syll. Algar. S: 657. 1907. 

 Farlovy. Notes on Fresh-Water Algae. Bot. Gaz. 8: 224. 1883. (R. f 1 u- 

 itans Cohn); 8: 246. 1883. (Echinella articulata Ag.). Wit- 



trock and Nordstedt. Algae. Aq. Dulc. Exsicc. no. 664. 1884. Wolle. 



Fresh- Water Algae U. S. 249. pi. 179. f. 4. 1887. Richter. Bot. Gaz. ig: 

 425. 1894. Tilden. List of Fresh-Water Algae collected in Minnesota 

 (luring 1894. Minn. Bot. Studies, i: 236. 1895. Collins, Holden and Setch- 

 ell. Phyc. Bor.-Am. Fasc. 7. no. 311. 1897. (G 1. pisum (Ag.) Thur.). 

 Howe. A Note on the "Flowering" of the Lakes in the Adirondacks. Tor- 

 reya. 3: 150. 1903. 



Plate XX. fig. 4. 



Colonies solid, free swimming, soft, firm when dried, .5-1.5 mm. in 

 diameter, especially spherical, sometimes lenticular, straight or recurved, 

 cylindrical, with the surface villous from the protruding trichomes; fila- 

 ments radiately arranged, loosely associated; trichomes 8-10 mic. broad at 

 the base, ending in a long hair; lowjer cells spherical, those in the middle 

 of the trichome quadrate, upper cells long cylindrical, the end cell pointed; 

 cell contents showing sulphur granules or vacuoles; heterocysts 9-10 mic. 

 in diameter, oblong or spherical; gonidia 8-18 mic. in diameter, 44-50 mic. 

 in length, cylindrical, straight or slightly curved, with granular contents. 



New York. Honnedaga Lake, Herkimer County. Altitude 2,200 feet. 

 August; Chilson Lake, Essex County, June to August. (Smith). Minne- 

 sota. Lake Sakatah and Lake Tetonka, Waterville. (Porter). Lake Minne- 

 tonka. August 1883; Waterville, June 1884. (Arthur). Lake Minnetonka. 

 August 1883. (Farlow). Lake Chisago, Chisago County. July 1894. (Mac- 

 Dougal and Anderson). 



Note : See also the two articles by Professor Arthur under R. pisum. 



522. Rivularia polyotis (Agardh) Bornet and Flahault. Revis. des Nos- 



toc. Ann. Sci. Nat. Bot. VII. 4: 360. 1886. De Toni. Syll. Algar. 

 S: 659. 1907. 

 Collins. Algae from Atlantic City, N. J. Bull. Torr. Bot. Club. 15: 310. 



