328 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



1858, p. 92 ; Farlow, 1881, p. 49. Filaments usually pale green, 

 forming expansions on ground or rocks in the literal zone ; cells 

 usually 20-25 /j. diatn., rarely a little more or less, length one or 

 two diameters. 



A very common plant on both Atlantic and Pacific coasts, 

 and probably in arctic and temperate regions the' world over ; 

 occurs also inland, near salt springs. Three varieties are to be 

 recognized ; there is no typical form distinct from these. 



Var. IMPLEXUM (Dillw.) Rosenvinge, 1893, p. 915, fig. 34; 

 P. B.-A., Nos. 266,^976. Forming a thin fleece on mud and 

 sand in the literal zone ; branches few or none. Greenland to 

 N. J., Alaska to Wash. Europe. 



Var. POLYRHIZUM (L,yng.) Rosenvinge, 1893, p. 915, fig. 32 ; 

 P. B.-A., No. 24. Sometimes found in the same localities as 

 the preceding variety, but more commonly on perpendicular 

 cliffs, where it hangs in skeins, attaching itself to the rock by 

 numerous branches of one to few cells each. Greenland to 

 Conn. ; Cal. J^urope. 



Var. VALIDUM (Gobi) Foslie in Wittr. and Nordst., Alg. 

 Kxsicc., No. 624. Filaments stouter than in the type, 30-50 /A 

 diam., branches frequently unicellular, often continuous with 

 the filament cell. Greenland. Northern Europe. 



Rhizoclonium lanosum Crouan in Maze and Schramm, 1870- 

 77, p. 53, No. 1179, and Chaetomorpha submaiina Crouan, I.e., 

 p. 52, No. 342, from authentic specimens, seem to belong under 

 R. riparium ; Chaetomorpha lanosa Crouan, I.e., p. 51, No. 251, 

 is more slender, 10-15 M diam., and seems to approach R. Kochi- 

 anum Kiitzing. 



4. R. TORTUOSUM Kiitzing, 1845, p. 206 ; Farlow, 1881, p. 

 49 ; P. B.-A., No. 23 ; Chaetomorpha tortuosa Harvey, 1858, p. 

 88, PI. XL/VI.B. Filaments dark green, 40-70 p. diam., cells 

 1-2 diam. long, forming curled and twisted masses in tide pools 

 and similar localities. Common frojn Gaspe to N. Y. ; reported 

 from W. I. ; Alaska to Washington. Europe. 



Found mostly in summer on exposed shores, where the dark 

 green crisped masses are very common in the lower pools ; it is 

 the Chaetomorpha tortuosa of Harvey, 1858, but hardly the 

 species of that name in Hauck, 1885, p. 443. The type is 

 without branches. 



Forma POLYRHIZUM Holden, P. B.-A, No. 625. With abun- 

 dant rhizoidal branches, of one to several short cells, similar to 



