Myxophyceae 227 



False branches in pairs, included within a common sheath as far as 

 the apex; gonidia spherical or oval; wall of gonidium deep brown. 



New York. Common on rocks exposed to spray. Niagara Falls. 

 (Wolle). 



418. Scytonema densum (A. Braun) Bornet in Bornet and Thuret. Notes 



Algologiques. 152. 1880. Bornet and Flahault. Revis. des Nostoc. 



Ann. Sci. Nat. Bot. VII. 5: 109. 1887. De Toni. Syll. Algar. 5: 



527. 1907. 

 West and West. On some Freshwater Algae from the West Indies. 

 Journ. Linn. Soc. Bot. 30: 271. 1895. Setchell. Notes on Cyanophyceae. — 

 II. Erythea. 4: 191. 1896; Notes on Cyanophyceae. — III. Erythea. 7: 48. 1899. 

 Collins. The Algae of Jamaica. Proc. Am. Acad. Arts Sci. 37: 241. 1901. 



Plate XIII. fig. 13. 



Plant mass dense, cushion-shaped, brown or black; filaments 24-40 mic. 

 in diameter, i mm. in length, entangled; false branches erect, appressed; 

 sheaths yellowish brown, gelatinous, lamellose, the younger ones pale 

 yellow; trichomes 6-12 mic. in diameter; heterocysts somewhat quadrate; 

 cell contents green. 



New York. On rocks. Niagara. August 1876. (Wolle). California. 

 Twin Oaks, San Diego County. (Koch). West Indies. Amongst S. 



J a V a n i c u m on lime-trees. Shanford Estate, Dominica. November and 

 December 1892. (Elliott). In turfs in moist places. Port Antonio, Jamaica. 

 April 1893. (Humphrey). 



419. Symphyosiphon bornetianum Wolle. Fresh-Water Algae U. S. 261. 



pi. 189. f. 4. 1887. De Toni. Syll. Algar. 5: 536. 1907. 



Plate XIII. fig. 14. 



Plant mass thin, with smooth surface, brownish or reddish brown; 

 filaments 12-15 mic. in diameter, short, thick, with the branches forming 

 a close, upright growth; sheaths close; cells somewhat longer or shorter 

 than the diameter; heterocysts scattered, yellowish; cell contents brown 

 or slightly blue-green. 



South Carolina. On old bricks. Port Royal; on clay cliffs. (Wolle). 



420. Scytonema dubium Wood. Contr. Hist. Fresh-Water Algae North 

 America. 63. pi. 6. f. 3- 1872. De Toni. Syll. Algar. 5: 533- i907- 

 Plant mass immersed; filaments 6-10 mic. in diameter, very long, 



closely interwoven, variously curved, usually sparingly branched; false 

 branches usually single, more or less distant, moderately short, some- 

 times very short, abortive and somewhat crowded; sheaths close, usually 

 rather thick and firm, transparent, colorless; trichomes often contained 

 in distinct, cell-like apartments, sometimes continuous, with indistinct trans- 

 verse walls; heterocysts cylindrical, two to six times longer than broad; 

 cell contents finely granular, usually pale bluish green, sometimes bright 

 blue-green. 



New Jersey. On leaves of Ranunculus aquatilis. In Shepherd's 



