242 Minnesota Algae 



Plate XV. fig. 6, 7. 



Primary filaments 7-10 mic. in diameter, flexuous, here and there 

 branched on one side, formed from a single row of cells; sheaths close, 

 thin, colorless; branches short, resembling the primary filaments, but more 

 slender; cells 7-9.5 mic. in diameter, 7-19 mic. in length; heterocysts 6-9 mic. 

 in diameter, 9-1 1 mic. in length, quadrate or oblong, intercalary. 



West Indies. On trees. Summit of Trois Pitons (4,500 feet), Dominica. 

 November, December 1892. (Elliott). 



Genus FISCHERELLA (Bornet and Flahault) Gomont. 

 Journ. de Bot. i. 1895. 



Plant mass forming a continuous, more or less expanded layer, ter- 

 restrial; filaments of two kinds; primary filaments creeping, containing one 

 or two rows of cells, unilaterally very much branched; branches or sec- 

 ondary filaments erect, elongate, more slender than the primary, contain- 

 ing very long hormogones within the sheath. 



I Plants living in moist places; primary filaments 6-9 mic. in diameter 



F. ambigua 



II Plants living in moist places or in hot water; primary filaments 10-13 



mic. in diameter F. thermalis 



446. Fischerella ambigua (Naegeli) Gomont. Note sur le Scytonema am- 



biguum Kuetz. Morot. Journ. de Bot. 9: 49. pi. 3. 1895. Bornet and 



Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. S: 100. 1887. 



(Scytonema ambiguum Kg.). De Toni. Syll. Algar. 5: 



576. 1907. 



WoUe. Fresh-Water Algae U. S. 262. pi. 189. f. 2. 1887. (Symphyo- 



siphon ambiguum Naeg.). Collins. Algae of Middlesex County. 



13. 1888. West and West. On some Freshwater Algae from the West 



Indies. Journ. Linn. Soc. Bot. 30: 270. 1895; A Further Contribution to 



the Freshwater Algae of the West Indies. 1. c. 34: 286. 1899. Setchell 



and Gardner. Algae of Northwestern America. Univ. CSlif. Pub. Bot. i: 



196. 1903. Lemmerman. Algenfl. Sandwich.-Inseln. Bot. Jahrb. 34: 625. 



1905. 



Plate XV. fig. 8, g. 



Plant mass crustaceous, orbicular, up to i mm. in thickness, brown 

 becoming black; filaments 6-9 mic. in diameter, very slender, densely co- 

 alesced in vertical fascicles; false branches aggregated; sheaths gelatinous, 

 colorless, finally becoming brownish; trichomes 2-3 mic. in diameter, thicker 

 at the apices; cells and heterocysts elongate; hormogones very long; cell 

 contents pale greenish or yellowish brown. 



United States. Frequently intermingled with larger algae, on moist 

 rocks, wet earth, etc. (Wolle). Massachusetts. Newton. (Farlow). 



Mexico. (Lenormand). West Indies. On trees, summit of Trois Pitons 

 (4,500 feet). November, December 1892; on the ground, mostly in old 

 "Diablotia" holes, Morne Anglais (2,300 feet), July 1892; on banks near 



