226 Minnesota Algae 



branaceous expansions, the outer layers white, somewhat transparent, the 

 internal layers bright yellow, contracted at the heterocysts, very smooth 

 on the surface; trichomes 9-15 mic. in diameter; cells shorter than the 

 diameter; heterocysts spherical, brownish; cell contents blue-green or green. 

 New York. On dripping rocks under Biddle Stairs, Niagara Falls. 

 1849. (Harvey). "The only locality hitherto discovered for this plant is 

 on the high cliff, near the Cave of the Winds, Niagara Falls. 'Twas found 

 there twenty-five years since and it may be gathered there to-day." (Wolle). 

 Minnesota. On gravel bed of a quiet stream, the outlet of an old tank near 

 the Government Dam works. Near Minneapolis. October 1901. Hone. 



416. Scytonema junipericolum Farlow in Collins, Holden and Setchell. 



Phyc. Bor.-Am. Fasc. 16. no. 756. 1900. De Toni. Syll. Algar. 

 S: 525. 1907. 



Plant mass forming indefinite, pulvinate, tomentose, black expansions 

 .2-.3 mm. high; basal filaments .14-16 mic. in diameter, nearly prostrate; 

 upper filaments 12-14 ™ic. in diameter; false branches in pairs, numerous, 

 erect, soon dividing into Tolypothrix-like, tortuous, corymbose branch- 

 lets; sheaths about 2 mic. in thickness, lamellose, with diverging layers, 

 with obtuse apex; cells at the base disc-shaped, the upper ones becoming 

 cuboidal and often torulose; heterocysts 11-12 mic. in diameter, 6-7 mic. 

 in length. 



Bermudas. Common, forming dark velvety patches on the bark of 

 Juniperus bermudiana. "Fairyland." January 1900. (Farlow). 



417. Scytonema crustaceum Agardh. Syst. Algar. 39. 1824. Bornet and 



Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 5: 106. 1887. 

 De Toni. Syll. Algar. 5: 525. 1907. 



Wolle. Fresh-Water Algae U. S. 263. 1887. (Symphyosiphon 

 crustaceus Kg.) Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 

 28. no. 1358. 1907. 



Plate XIII. fig. 10-12. 



Plant mass cushion-shaped, black, .5-2 mm. in thickness; filaments 

 15-30 mic. in diameter, thick, short, erect, aggregated, often slightly thick- 

 ened and decumbent, with numerous branches; false branches ascending, 

 short, in pairs, coalesced at the base, finally becoming free; sheaths gelati- 

 nous, yellowish brown, lamellose, the layers diverging; trichomes 6-8 mic. 

 in diameter; cells somewhat quadrate or depressed; heterocysts oblong, 

 blue-green. 



Connecticut. On limestone rock. Salisbury. November 1906. (Phelps). 

 Pennsylvania. Not infrequent, on wet cliffs. (Wolle). 



Var. incrustans (Kuetzing) Bornet and Flahault. 1. c. 107. De Toni. 

 1. c. 526. 



Wolle. Fresh Water Algae. II. Bull. Torr. Bot. Club. 6: 139. 1877; 

 (Symphyosiphon incrustans Kg.). A Nostoc the Matrix of 

 Scytonema. Bull. Torr. Bot. Club. 217. 1878. Setchell. Notes on Cyano- 

 phyceae. — II. Erythea. 4: 191. 1896. 



