Myxophyceae 289 



lamellpse, ocreate, hyaline or brownish; ocreae funnel-shaped, dilated above; 

 trichomes .9-12.5 mic. in diameter, gradually tapering into a thick hair with 

 short cells; lower cells somewhat quadrate, upper cells three or four times 

 shorter than their diameter; heterocysts oblong or hemispherical. 



Massachusetts. Spot Pond, Stoneham. (Collins). Minnesota. "Very 

 abundant, covering the surface of the lake for a considerable extent. The 

 natives consider it to be grass seed washed into the lake." July 1880. 

 (Hobbe). Iowa. In West Okoboji Lake, Dickinson County. (Stalker). 

 Montana. On water plants. 1874. (Kuntze). 



527. Rivularia paradoxa (WoUe) De Toni. Syll. Algar. 5: 672. 1907. Wolle. 



Fresh Water Algae. II. Bull. Torr. Bot. Club. 6: 138. 1877. (Z o n o- 

 trichia paradoxa Wolle); Fresh Water Algae. III. 1. c. 184. 



Colonies hemispherical, gelatinous, bright blue-green; younger fila- 

 ments flagelliform, older ones often contracted in the middle, or narrow 

 below and gradually widened more than half the length, then tapering to 

 a fine point (filaments of the latter form are usually much longer, double 

 the length of the former); trichomes continuous or indistinctly divided; 

 cells quadrate to three '/imes as long as wide, very variable; cell contents 

 >.Tanular, green tinged with brown; heterocysts 10-12 mic. in diameter. 



Pennsylvania. Wolle. 



528. Rivularia atra Roth. Catalecta Botanica. 3: 340. 1806. Bornet 'and 



Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 4: 353. 1886, 



De Toni. Syll. Algar. 5: 664. 1907. 

 Wood. Contr. Hist. Fresh-Water Algae North America. 50. 1872. 

 (,2. onotrichia minutula Rab.). Farlow. List Marine Algae United 

 States. Proc. Am. Acad. Arts Sci. 10: 380. 1875. Farlow. Marine Algae of 

 New England. 38. pi. 2. f. 2. 1881. Kjellman. Algae of the Arctic Sea. 321. 

 1883. (Rivularia hemispherica (L.) Aresch). Farlow. Notes on 

 Fresh-Water Algae. Bot. Gaz. 8: 224. 1883. Pike. Check List of Marine 

 Algae. Bull. Torr. Bot. Club. 13: 106. 1886. Collins. Marine Algae of 

 Nantucket. 5. 1888. Wolle and Martindale. Algae. Britton's Catalogue 

 of Plants found in New Jersey. Geol. Surv. N. J. 2: 604. i88g. Martindale. 

 Marine Algae of the New Jersey Coast and Adjacent Waters of Staten 

 Island. Mem. Torr. Bot. Club, i: 91. 1889. Anderson. List of California 

 Marine Algae, with Notes Zoe. 2: 218. 1891. Collins. Algae. — Rand and 

 Redfield's Flora of Mount Desert Island, Maine. 247. 1894. Rosenvinge. 

 Les Algues Marines du Groenland. Ann. Sci. Nat. Bot. VII. 19: 162. 1894 

 Collins, Holden and Setchell. Phyc. Bor.-Am. Fiasc. 8. no. 357. 1897. Ros- 

 envinge. Deuxieme Memoire sur les Algues Marines du Groenland. Medd. 

 om Groenland. 20: 121. 1898. Collins. Preliminary Lists of New England 

 Plants. — V. Marine Algae. Rhodora. 2: 43. 1900; Phycological Notes of tho 

 late Isaac Holden.— II. Rhodora. 7: 224. 1905. Borgesen and Jonsson. 

 The Distribution of the Marine Algae of the Arctic Sea and of the North 

 ernmost Part of the Atlantic. Bot. Faeroes. App. XXV. 1905. 



Plate XX. fig. 10. 

 Colonies up to 4 mm. in diameter, spherical, solitary or -confluent, dark 



