178 Minnesota Algae 



separate or aggregated, sometimes proliferated, surrounded by a firm, 

 tenacious outer layer, blue-green, sky blue, or becoming brownish, 

 pellucid; filaments densely interwoven, flexuously twisted; sheaths usually 

 indistinct; trichomes 5-7 mic. in diameter, twisted; cells barrel-shaped; 

 heterocysts 8-10 mic. in diameter, spherical or depressed spherical; go- 

 nidia unknown. 



New Jersey. Growing attached to moss. Northern part of state. (Aus- 

 tin). Minnesota. In small stagnant pools at edge of lake. Parker's 

 Lake, Hennepin County. July 1894. (Tilden). Floating in great quantities. 

 Lake Zumbra. September 1903. (Butler). Iowa. Ames. 1884. (Bessey). 

 Washington. In a ditch of fresh water. Near Seattle. (Gardner). 



335. Nostoc pruniforme (Linn.) Agardh. Dispositio Algar. Sueciae. 45. 



1812. Bornet and Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. 



VII. 7: 215. 1888. De Toni. Syll. Algar. 5: 418. 1907. 

 Wood. Contr. Hist. Fresh-Water Algae North America. 28. 1872. 

 Wolle. Fresh Water Algae. III. Bull. Torr. Bot. Club. 6: 183. 1877. Rab- 

 enhorst. Die Algen Europas. no. 2530. 1878. Twitchell. Remarks on a 

 Variety of Nostoc pruniforme. Journ. Cin. Soc. Nat. Hist. 9: 253. 1886. 

 Wolle. Fresh- Water Algae U. S. 284. 1887. Atwell. A Deep-Water Nos- 

 toc. Bot. Gaz. 14: 291. 1889. Wolle and Martindale. Algae. Britton's 

 Catalogue of Plants found in New Jersey. Geol. Surv. N. J. 2: 606. 1889. 

 Johnson and Atwell. Fresh Water Algae. Northwestern University. Report 

 Dept. Nat. Hist. 21. 1890. Saunders. Protophyta-Phycophyta. Flora of 

 Nebraska. 18. pi. i. f. 4. a, b. 1894. Tilden. List of Fresh-Water Algae 

 collected in Minnesota during 1893. Minn. Bot. Studies, i: 31. 1894; Amer- 

 ican Algae. Cent. I. no. 85. 1894; List of Fresh-Water Algae collected in 

 Minnesota during 1894. Minn. Bot. Studies, i: 236. 1895. Collins, Holden 

 and Setchell. Phyc. Bor.-Am. Fasc. 2. no. 58. 1895; 1. c. Fasc. 14. no. 657. 

 1900. Setchell and Gardner. Algae of Northwestern America. Univ. 



Calif. Pub. Bot. i: 191. 1903. Collins. Phycological Notes of the late 

 Isaac Holden. II. 7: 237. 1905. Buchanan. Notes on the Algae of Iowa. 

 Proc. Iowa Acad. Sci. 14: 11.^ 1908. 



Plate VIII. fig. 9, 10. 



Colonies spherical, attaining the size of a hen's egg, soft and watery 

 within, at length hollow, surrounded by a leathery outer layer, olive or 

 dark blue-green, finally becoming brownish or blackish; filaments loosely 

 entangled, radiating from the center; sheaths often distinct, colorless, rarely 

 yellowish; trichomes 4-6 mic. in diameter, cells spherical compressed or a 

 little longer than the diameter; heterocysts 6-7 mic. in diameter, somewhat 

 spherical. 



Maine. (Leidy). Connecticut. In a stagnant pool connected with 

 the lower of "Twin Lakes," mostly resting on the bottom, but attached 

 when young to sticks, etc., growing to the diameter of about 5 cm. Salis- 

 bury, Litchfield County. August 1895. (Holden). New Jersey. In ponds, 

 frequent. (Wolle). Pennsylvania. In stagnant water. Bethlehem. 1877. 

 (Wolle). Illinois. "With the first gales of November and March each 

 year there appears upon the shore of Lake Michigan, an abundance of 



