NOSTOCE^E. 277 



broad, aeruginous ; sheath of stein rather ample, often yel 

 lowish brown ; of branchlets, thin, close, colorless, hyaline. 



Diameter of filaments, 15 //, more or less. 



Very near H. byssoideus, but more slender, cells longer, 

 and aquatic, parasitic on water plants ; appears to stand be- 

 tween H. byssoideus and //. Braunil. 



Plate CXCVI, fig. 1, after a specimen from Dennisville, 

 New Jersey. 



HAPALOSIPHON FUSCESCENS, Kg. 



Floccose caespitose, dull aeruginous, changing to lighter 

 or darker olive brown, parasitic ; much branched ; usually 

 internal trichome light aeruginous or light olive yellow, 

 more or less distinctly articulate, granular ; articles equal, 

 to two or more times longer than broad ; ends of branchlets 

 often somewhat SAvollen. 



Diameter of filaments, 8-11 /* ; branchlets, 5-7 yw. 

 Pond waters. 



Syn. Tolypoihrix pumila, Kg. ; T. fuscescens, Breb. 



Differs from If. Braunii in its more slender filaments, and 

 longer cells. 



Plate CXCVI, figs. 22, 23, specimens from ponds, New 

 Jersey. 



HAPALOSIPHON TENUISSIMTJS, Grun. 



Parasitic, floccose, irregularly, squarrosely branched. 

 Branches internally, pale aeruginous, often interrupted, in- 

 distinctly articulate, variously curved; sheath thin and 

 close, colorless. 



Diameter of sterns, about 7-8 IJL ; branchlets about half 



as thick. 



Ponds and wet ground. 



Plate CXCVI, figs. 20, 21, specimens from pond, New 

 Jersey ; not infrequent also in Pennsylvania, Minnesota, 

 Florida ; no doubt widely distributed. 



SECTION IV. NOSTOCE^E. 



Simple, branchless filaments, with or without a sheath, never 

 terminating with a hair-point, always provided with heterocysts. 

 Spores usually present in mature filaments. 



Multiplication takes place in a two -fold manner. First, by 

 means of the spores which give rise to young plants ; and sec- 

 ondly, by means of hormogons, or parts of internal trichomes 

 which separate from the filaments and develop new plants. 



