THE GREEN ALGAE OF NORTH AMERICA 201 



A coarse species, readily recognized by its habit. It appears 

 to be not uncommon on the southern part of the Atlantic coast, 

 but rare in New England. The color is usually a rather deep 

 or dark green ; the main branches are quite long, and are 

 everywhere beset with short, tapering ramuli ; the cells are 

 rounded, almost entirely occupied by the chromatophore ; with- 

 out any definite arrangement, except in the ramuli. 



10. E. COMPRESSA (L.) Greville, 1830, p. 180, PI. XVIII. 

 Frond tubular, more or less compressed, sometimes constricted, 

 varying much in dimensions ; branches usually simple, cylin- 

 drical or expanding above, in either case narrowed at the base, 

 similar in appearance to the main stem ; cells in no definite 

 order; membrane rather thin. Greenland to N. J.; Alaska to 

 Cal. Europe, So, America, Tasmania. 



A variable species, but now understood in a narrower sense 

 than formerly, and including only forms with branches con- 

 tracted at the base, with cells 10-15 /j. diam., arranged in no 

 definite order, and with membrane not thickened. 



Forma SUBSIMPLEX J. G. Agardh, 1882, p. 137; P. B.-A., 

 No. 964. Frond hardly branched, of uniform diameter. Me. 



Europe. 



11. E. MINIMA Nageli in Kiitzing, 1849, p. 482 ; 1856, p. 

 16, PI. XLIU, fig. 3; P. B.-A., Nos. 468, 912. Frond i-io 

 cm. long, 1-5 mm. broad, simple or slightly proliferous, soft and 

 delicate, membrane 8-10 /u. thick, cells angular, 5-7 p. diam., 

 arranged in no definite order. Greenland to Conn.; Alaska to 

 Mexico. Europe, So. Pacific. 



A small species, resembling E. compressa, but smaller in di- 

 mensions of fronds and size of cells. It is probably common, 

 but is easily overlooked among the larger and better known 

 species of the genus. The extreme thinness of the frond gives 

 it a very soft and delicate feeling to the touch, which is the best 

 character by which to recognize it when growing. It seems to 

 grow mostly in the lower half of the literal zone. 



Forma RIVULARIS Collins, P. B.-A., No. XXVI. Color pale, 

 fronds to half a meter in length, substance more delicate than in 

 the type. These differences are probably due to its place of 

 growth, running fresh water. Alaska. 



Forma GLACIAUS Kjellman, 1877, p. 50; P. B.-A., No. 

 1183. Frond 9-13^ thick; cells 5-8 p. diam.; forming a dense 



