262 FRESH-WATER ALG^E OF THE UNITED STATES. 



Plate CLXXXIX, fig. 7, the normal growth, moderately 

 magnified ; fig. 8, single filaments separated from a bundle, 

 much enlarged. 



SYMPHYOSIPHON CASTELLI, (Mass.) Rab. 



Forms a dark, black coating, pulviuate, on wet rocks, 

 surface pubescent, or hirsute by the projecting ends of the 

 filaments. Trichomes sparsely branched, somewhat curved ; 

 internal trichomes aeruginous, shortly articulate, not toru- 

 lose, 2-4 articles to a diameter, often interrupted by the in- 

 clining of the short cells. Sheath close, firm, colorless. 

 Heterocysts rather square with angles rounded. 



Diameter of filaments, 9-15 /./. 



Plate CLXXXIX, fig. 1, filaments occur more or less in 

 cluster of 30-50. This imperfectly represents one such 

 cluster. 



SYMPHYOSIPHON HOFMANNI, ( Ag. ) Kg. 



Terrestrial, resembling a Symploca in habit. Tufts small, 

 ascending, dark brown ; trichomes simple, erect, loosely 

 collected in pointed fascicles, internally pale aeruginous 

 green, sometimes interrupted, joints delicately granulose ; 

 inferior cylindrical, thin; superior thicker and sometimes 

 more or less swollen. Sheath wider at the base, close above, 

 indistinct, colorless or yellowish. Heterocysts intercalated, 

 globose, hyaline. 



Diameter of filaments, 8-12 yu. 



Occurs not only on the ground ; have found good speci- 

 mens on old wood. 



Plate CLXXXIX, fig. 3, a simple cluster, ends not always 

 so spreading. 



SYMPHYOSIPHON AMBIGUUM. Naeg. 



Stratum somewhat crustaceous, extended, dark fuscous. 

 Trichomes fasciculately clustered. Internal filament dilute 

 aeruginous, distinctly or indistinctly articulate, finely gran- 

 ulate, articles short, one-half diameter or less ; sheaths close, 

 colorless, sometimes with a yellow tinge. 



Diameter of filaments, 5-7 yw. 



Frequently intermingled with larger alg&e on moist rocks, 

 wet earth, etc. 



Plate CLXXXIX, fig. 2. 



