526 University of California Puhlications in Botany [Vol. 8 



Growing on species of Rhodomela and Odonthalia, frequently in 

 tide pools, in the littoral belt. Common along the whole coast from 

 Unalaska, Alaska, to southern California. 



Postels and Ruprecht, Illus. Alg., 1840, p. 19 ; Kjellman, Om 

 Beringh. Algfl., 1889, p. 47, pi. 7, figs. 4, 5; Saunders, Ph-yc. Mem. 

 1898, p. 165, pi. 29, figs. 4, 5 ; Setchell and Gardner, Alg. N.W. Amer., 

 1903, p. 244. ■ 



Two forms have been segregated as follows : 



Soranthera nlvoidea f. typica S. and G, 



Plate 39, figs. 40, 41, and plate 836 



Fronds nearly regular in outline, membrane thicker, oval to 

 spherical, up to 7 cm. diam. 



Growing on species of Rhodomela and Odonthalia. From Pacific 

 Grove, California, northward into Bering Sea, and more common in 

 the southern part of the range than f . dijformis. 



Setchell and Gardner, lac cit.; Kjellman, loc. cit.; Saunders, loc. 

 cit., Alg. Harriman Exp,, 1901, p. 422 ; Collins, Holden and Setchell, 

 Phyc. Bor.-Amer. (Exsicc), no. 417; Tilden, Amer. Alg. (Exsicc), 

 no. 245. 



Soranthera ulvoidea f. difformis S. and G. 



Fronds gregarious, membrane thinner, usually smaller than the 

 above, variously and deeply lobed. 



Growing on the same hosts as the two preceding, but is more 

 common on the northern part of the range, from Cape Platterj^ 

 northward. 



Setchell and Gardner, Joe. cit.; Collins, Holden and Setchell, loc. 

 cit., no. 1130. 



Forma difformis seems to prefer either brackish or muddy water or 

 is induced by such medium. 



Soranthera ulvoidea Post, and Rupr. is a very common species 

 along the entire Pacific coast of North America from Pacific Grove, 

 California, northward. Careful search has failed to reveal the 

 gametangia. 



