THE GREEN ALGAE OF NORTH AMERICA 185 



filaments; cells cylindrical or somewhat swollen, y$-i l /> diam. 

 long when full grown, longer in young filaments ; cell wall at 

 first thin, growing thicker ; chromatophore a broad or narrow 

 band at the middle of the cell, with several large pyrenoids. 

 Fig. 64. Greenland, Northern U. S. from Me. to Alaska. 



I Europe. 



A common species in spring, attached to sticks or stones in 

 streams or pools ; the filaments are nearly the same diameter 

 throughout, or smallest at the base, considerably larger above ; 

 the cells are usually actually as well as relatively longer near 

 the base. It is not likely to be mistaken for other fresh water 

 species of Ulothrix, but it is not unlike Microspora -crassior and 

 M. amocna, which occur in similar stations. The characters of 

 the chromatophores and of the cell wall can be depended on for 

 distinction in the living plant. 



9. U. IMPLEXA Kiitzing, 1849, p. 349; 1852, PI. XCIV, 

 fig. 2 ; Hazen, 1902, p. 153, PI. XXI, figs, i and 2 ; P. B.-A., 

 No. 115. Forming light green, soft masses, cells 6-15 //, diam., 

 sometimes slightly swollen at the middle, about as long as 

 broad, chromatophore occupying only the middle part of the 

 cell, often an incomplete ring. Atlantic coast and Alaska. 



Europe. 



Rather common from New Jersey to Greenland, usually near 

 high water mark, and where it is more or less exposed to the in- 

 fluence of fresh water ; most frequent in spring. Reported from 

 Florida by Wolle, but the identification is doubtful. 



10. U. FLACCA (Dillw.) Thuret in Le Jolis, 1863, p. 56; 

 Farlow, 1881, p. 45; Hazen, 1902, p. 155, PI. XX, figs. 7-9; 

 P. B.-A., Nos. 17, 1123; Hormotrichum spetiosum and ff. bore- 

 ale Harvey, 1858, p. 90. Forming bright or dark green, often 

 much entangled masses or skeins ; cells 10-25 P- diam., J4~H a & 

 long as broad ; when producing spores up to 50 /x broad, and 

 swollen in the middle ; chromatophore occupying the whole of 

 the cell wall. Atlantic and Pacific coasts. Europe. 



Common between tide marks from New Jersey to Greenland, 

 and occurring on the Pacific coast from Washington to Califor- 

 nia ; in southern New England chiefly on Fucus and Spartina 

 (Hazen, 1902, p. 156) ; more northerly, abundant on rocks and 

 woodwork, often forming, in company with Hormisda penicilli- 

 formis and Bangia fusco-purpurea , a band along the shore be- 



