i6o Minnesota Algae 



According to Wille, Oscillatoria capitata West should be 

 made a variety of this species: 



Var. capitata Wille. Die Schizophyceen der Plankton-Expedition. 52. 

 pi. I. f. 8, 9. 1904. 



Plate VI. fig. 34- 



Filaments irregularly wound or twisted within an oval gelatinous en- 

 velope; trichomes 10-14 mic. in diameter. 



West Indies. Lat. 23° 44' N.; long. 45° 30' W. (Murray and Black- 

 man). 



Genus HALIARACHNE Lemmermann. 

 Planktonalg. Ergebn. einer Reise n. d. Pacific. 353. 1899. 



Filaments multicellular, floating free, in somewhat globose or elon- 

 gate, gelatinous colonies, arranged in two layers, radiating from the cen- 

 ter, hooked at the apex; reproduction by division of the colony. 



308. Haliarachne lenticularis Lemmermann. Planktonalgen. Ergebnisse 

 einer Reise nach dem Pacific. Abhandl. d. naturw. Verein in Brem- 

 en. 353. pl. 2. f. 22-24. 1899; Algenfl. Sandwich.-Inseln. Bot. Jahrb. 

 34: 619. 1905. De Toni. Syll. Algar. 5: 385. 1907. 

 Colony lenticular, 450-700 mic. in diameter; apical cell possessing a 

 calyptra; cells about 8 mic. in diameter, 4-7 mic. in length; cell contents 

 showing gas vacuoles. 



Hawaii. In plankton, between the islands of Lay'san and Hawaii. 1896- 

 97. (Schauinsland). 



Family II. NOSTOCACEAE 



Sheaths forming a more or less distinct mucous, gelatinous or mem- 

 branaceous tegument, mostly confluent, often not present; trichomes con- 

 sisting of a single row of uniform cells, with heterocysts, usually twisting 

 and entangled, not branched, showing no differentiation of base and apex, 

 reproduction by means of vegetative division, hormogones and gonidia. 



I. Sheaths inconspicuous, or mucous and diffluent, or gelatinous, firm and 

 thick 



1 Trichomes flexuous and contorted, forming a plant mass or colony 



of definite shape 

 (i) Colony usually of a rounded or expanded character, gelati- 

 nous, made up of dissolved individual sheaths, attached to the 

 substratum or floating free in water; heterocysts intercalary 



Nostoc 

 (2) Colony tubular, cylindrical; filaments somewhat straight, parallel, 

 agglutinated WoUea • 



2 Trichomes more or less straight, free, or forming a thin mucous 



layer of indefinite shape 



