5.8-8/A in diameter, 11.7-15ju, long; sheath thin, colorless, and not 

 lamellate; filament 7.5-10- ( 12 )/x wide. 



Like other species in this genus, H. hibernicus seems to be con- 

 fined to shallow water where there is a concentration of organic 

 matter and considerable bacterial decomposition in progress. 



Among other algae in soft water lakes. Wis. 



Hapalosiphon intricatus West & West 1895b, p. 271 



PI. 129, Fig. 1 

 Trichomes with unilateral, rather short branches which are 

 flexuous, densely entangled, and equal in diameter to the main? 

 filament; sheaths close; cells ovate, barrel-shaped or short-cylindric, 

 3.8-6.8- ( 7.2 )/x in diameter. 



Forming a blue-green weft over Sphagnum; in swampy margins 

 of lakes. Wis. 



Hapalosiphon pumilus ( Kuetz. ) Kirchner 1878, p. 231 

 PI. 129, Figs. 2-4 



Filaments prostrate and much entangled, forming dense and very 

 extensive mats on submerged aquatics, freely branching, the 

 branches arising mostly unilaterally; cells globose, quadrate or 

 short-cylindric, 6-lOju in diameter, 1-3 times the diameter in length; 

 heterocysts short- or long-cylindric, 10/a in diameter, 12-22ju, long; 

 sheath thin in the older parts of the plant, lamellate, either hyaline 

 or yellow-brown; main filament, 12-25ju, wide, branches 10-15;u wide. 



Common in shallow water at margins of reed-filled lakes and in 

 acid swamps. In the latter habitat this species may be the dominant 

 form, producing brown cottony mats and clots about culms of 

 rushes, dead grasses, etc., sometimes acres in extent. Mich., Wis. 



The characteristics of this plant are best determined by studying 

 the older portions of the plant. Young branchings show color, cell- 

 shape and sheath characters unlike the main body of the plant and, 

 when isolated, may become identified as some of the other species 

 of Hapalosiphon. Indeed, it is possible that some of the names and 

 descriptions applied to expressions of Hapalosiphon may be based 

 on young portions of H. pumilus. See notes on H. aureus above. 



STIGONEMA C. A. Agardh 1824, p. xxii 

 Multiseriate (rarely uniseriate), branched and irregularly spread- 

 ing filaments with wide, firm, mucilaginous sheaths which may be 

 either homogeneous or lamellated, hyaline or colored; plants either 

 scattered among other algae or forming cushion-like clumps or 

 turfy patches, free-floating, or on soil and moist substrates; cells 



[546] 



