THE GREEN ALGAE OF NORTH AMERICA 203 



/A thick, not much exceeding the dimensions of the cells in cross 

 section. Greenland to W. I. ; Alaska to Cal. Europe. 



A common species, formerly included in E. compressa or E. 

 intestinalis, to the former of which it is most allied, but from 

 which it differs in the longitudinally seriate cells, very manifest 

 in the younger portions, and disappearing only in the quite old 

 parts. In habit it is very variable, from slender, slightly 

 branched forms, only a few cm. long, to richly and repeatedly 

 branched fronds ; branches sometimes long and slender, some- 

 times short and very densely set, sometimes long and short 

 intermingled quite without order. It appears to prefer some- 

 what sheltered localities where it is not left bare for any consid- 

 erable time at low tide. It is found in fresh water in several 

 stations in the western states, as well as about salt springs. 



Var. arctica (J. Ag.) nov. comb. ; E. arctica]. G. Agardh, 

 1882, p. 124, PI. IV, figs. 100-102. Cells smaller and rounded, 

 membrane 20-30/1 thick, cells 10-14 p. in cross section, usually 

 longer than broad, sometimes double their breadth. Green- 

 land. Spitsbergen. 



Var. TRABECULATA Rosenvinge, 1893, p. 961, fig. 55. More 

 slender than the type, with long, capillary branches ; the cen- 

 tral cavity traversed by transverse and oblique " trabeculae." 

 Greenland. 



Var. TUBULOSA (Ku'tz.) Reinbold, 1889, p. 117; P. B.-A., 

 No. 471. E. tubulosa Kiitzing, 1856, p. n, PI. XXXII, fig. 2. 

 Slender, slightly branched, of nearly uniform diameter through- 

 out. In ditches in marshes. Mass. ; Great Salt Lake, Utah ; 

 reported from Barbados. Europe. 



15. E. FLEXTJOSA (Wulf.) J. G. Agardh, 1882, p. 126; 

 P. B.-A., No. 462. Frond cylindrical, tubular, simple, taper- 

 ing to a filiform stipe below, above inflated, flexuous and intes- 

 tine-like ; cells 6-8X8-12 /*, roundish polygonal, in longitudinal 

 series ; membrane somewhat thickened on the inside ; chro- 

 matoph'ore filling the thick- walled cell. Fla., Southern Cal. 



Warmer waters generally. 



This is a southern species, and on our Florida shores appears 

 to take the place of E. intestinalis in the north. From the latter 

 it differs in having somewhat smaller cells, arranged in regular 

 series ; also somewhat more delicate membrane. From E. com- 

 pressa it is also distinguished by the arrangement of the cells, 



