2i6 Minnesota Algae 



.397. Scytonema azureum Tilden. American Algae. Cent. VII. Fasc. i. no. 

 630. 1909. 



Plate XII. fig. 2, 3. 



Filaments 25 mic. in diameter, flexuous, sparingly branched; false 

 branches usually in pairs, occasionally originating at the heterocysts as in 

 Tolypothrix; sheaths narrow, straight, smooth; trichomes 17 mic. 

 in diameter, often constricted at joints; cells quadrate or shorter than 

 broad; hetero.cysts somewhat spherical or quadrate, yellowish green; cell 

 contents more or less deep bluish purple (cyaneus, azureus) in color. 



Hawaii. With other algae forming a layer covering rocks on bottom 

 and sides of basin of "warm spring." Temperature at 7 a. m. 31 + ° C. 

 Puna, Hawaii. July 1900. (Tilden). 



398. Scytonema hofmanni Agardh. Synopsis Algar. Sueciae. 117. 1817. Bor- 

 net and Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 5: 

 97. 1887. De Toni. Syll. Algar. 5: 513. 1907. 

 Wood. Prodromus of a Study of the Fresh-Water Algae of Eastern 

 North America. 130. 1869. Maze and Schramm. Essai Class. Algues 



Guadeloupe. 32. 1870-1877. (S. j u 1 i a n u m Menegh., S. c i n e r e u m 

 Crouan). Wood. Contr. Hist. Fresh-Water Algae North America. (S. 

 cortex Wood). 64. 1872. Farlow. Notes on the Cryptogamic Flora of 

 the White Mountains. Appalachia. 3: 236. 1883. (Symphyosiphon 

 hofmanni Kg.). WoUe. Fresh- Water Algae U. S. 262. pi. 189. f. 3. 



1887. Moebius. Ueber einige in.Portorico gesammelte Siisswasser- und 

 Luft-Algen. Hedwigia. 27: 245. 1888. Wolle and Martindale. Algae. Brit- 

 ton's Catalogue of Plants found in New Jersey. Geol. Surv. N. J. 2: 605. 

 1889. Bessey. Additions to the Reported Flora of Nebraska, made dur- 

 ing 1893. Bot. Surv. Nebraska. 5. 1894. Saunders. Protophyta-Phycophyta. 

 Flora of Nejjraska. 24. 1894. Collins, Holden and Setchell. Phyc. Bor.- 

 Am. Fasc. 9. no. 404. 1898. West and West. A Further Contribution to 

 the Fresh-water Algae of the West Indies. Journ. Linn. Soc. Bot. 34: 287. 

 1898-1900. Collins. The Algae of Jamaica. Proc. Am. Acad. Arts Sci. 

 37: 241. 1901. Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 17. no. 

 803. 1901. Setchell and Gardner. Algae of Northwestern America. Univ. 

 Calif. Pub. Bot. i: 195. 1903. Collins. Phycological Notes of the late 



Isaac Holden. — II. Rhodora. 7: 237. 1903. Collins, Holden and Setchell. 

 Phyc. Bor.-Am. Fasc. 26. no. 1258. 1905. 



Plate XII. fig. 4. 



Plant mass cushion-shaped, widely expanded, 1-3 mm. in thickness, 

 blackish or blue-green, sometimes impregnated with calcium carbonate, 

 then purple or green or bluish gray; filaments 7-15 mic. in diameter, coa- 

 lesced in vertical fascicles; false branches aggregated; sheaths firm, mem- 

 branaceous; trichomes 5-10 mic. in diameter, olive or blue-green; cells un- 

 equal in length; heterocysts oblong. 



Alaska. On dripping rocks. Iliuliuk, Unalaska. (Setchell and Lawson). 

 New Hampshire. On rocks near the brook. Tuckerman's Ravine, near Shel- 



