Myxophyceae 291 



hair; lower cells twice as long as the diameter, those in the middle of ths 

 trichome quadrate, the upper ones half as long as wide. 



Arctic Regions. "Forming firm, gelatinous bosses on pebbles in running 

 water." In streams from a lake, winter-quarters. 82° 27' N., 61° 22' W. 

 (Moss). Canada. Forming a calcareous crust on botton of ditch. Natural 

 Sulphur Springs, Banfif, Alberta. 13 August 1897. (Tilden). New York. 

 Forming a slippery grayish, or grayish flesh-colored coating on rocks kept 

 wet and glistening with foam and spray. "Cave of the Winds," Niagara 

 Falls. (Wood). "Growing on rocks as glossy blackish, very hard and 

 slippery fronds or masses, which varied in size from that of very small 

 shot to nearly half an inch in length." (Wood). New Jersey. Rocky 

 margins of Green Pond, Morris. (Wolle). Pennsylvania. Stones. Sus- 

 quehanna River. (Wolle). Michigan. Grosse Isle, near the mouth of the 

 Detroit River. Summer of 1885. (Campbell). Nebraska. Minden. (Saun- 

 ders). Colorado. Forming a reddish crust upon dripping rocks. Bridal 

 Veil Falls, Williams Canon, near Manitou. (Setchell). 



530. Rivularia dura Roth. Neue Beitrage zur Botanik. 273. 1802. Bornet 



and Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 4: 347- 



1886. De Toni. Syll. Algar. 5: 674. 1907. 



Wood. Contr. Hist. Fresh-Water Algae North America. 50. pi. 4. f. 5. 



1872. (Dasyactis mollis Wood). Campbell. Plants of the Detroit 



River. Bull. Torr. Bot. Club. 13: 93. 1886. Wolle. Fresh- Water Algae U. 



S. 249. pi. 179. f. 1-3. 1887. Bennett. Plants of Rhode. Island. 114. 1888. 



Collins. Algae of Middlesex County. 13. 1888. (R. radians Thur.). 



Wolle and Martindale. Algae. Britten's Catalogue of Plants found in New 



Jersey. Geol. Surv. N. J. 2: 604. 1889. Mackenzie. A Preliminary List 



of Algae collected in the Neighborhood of Toronto. Proc. Can. Inst. III. 



7: 270. 1890. Snow. The Plankton Algae of Lake Erie. U. S. Fish 



Comm. Bull, for 1902. 22: 392. 1903. 



Plate XX. fig. IS. 



Colonies small, 5 mm. in diameter, somewhat hard, indurated with cal- 

 cium carbonate, blackish green; filaments dense; sheaths close, not lamel- 

 lose, uniform, hyaline; trichomes 4-9 mic. in diameter, ending in a long, 

 very thin hair; lower cells equal in length to the diameter, upper ones 

 almost three times shorter than wide; cell contents blue-green, sometimes 

 changing to violet when dried. 



Canada. High Park, Toronto. (Mackenzie). Massachusetts. (Col- 

 lins). Rhode Island. Not uncommon. (Bennett). New Jersey. At- 

 tached to aquatic plants in ponds. (Wolle). Ohio. Plankton. Lake Erie. 

 Put-in-Bay. (Snow). Michigan. Attached to water plants in a small bog 

 near mouth of Carp River in northern part of state. (Wood). Grosse Isle, 

 near the mouth of the Detroit River. Summer of 1885. (Campbell). 



531. Rivularia coadunata (Sommerfelt) Foslie. Contributions to Knowl- 

 edge of the Marine Algae of Norway. II. Tromsoe Mus. Aarsheft. 

 14: 21. 1891. Bornet and Flahault. Revis. des Nostoc. Ann. Sci. Nat. 



