1920] Seichell-Oardner : Chlorophyceae 171 



ture of the water at that point, we suspect that their plants may 

 belong rather to C. RiUeri than to C. mamillosum which is a sub- 

 tropical species. 



3. Codmm fragile (Suring.) Hariot ^' ^^ '^.j^olCZX^ ''^ 



Plates 28, 29 <:3^I.^Z<^^*^-7'2^^^ ' 



Fronds one to several from a broad spongy disk, cylindrical, 

 profusely and dichotomously branched, 25-40 cm. high, 2-10 mm. in 

 diameter, glossy, dark green, finely rugose on the surface or, at times, 

 densely" tomentose with long hyaline hairs; utricles cylindric claVate, 

 150-350/x, (occasionally 630ju.) in maximum diameter, and 5-10 times 

 as long as broad, provided (at least when young) with a more or 

 less distinct mucro; gametangia (2 ?) fusiform, 1-3 to each utricle, 

 250-450^ long and 75-150yLi in diameter. 



Growing on exposed rocks and in small pools in the littoral belt. 

 Alaska to Mexico. 



Hariot, Algues du Cap Horn, 1889, p. 32 ; De-Toni, Phyc. Japon. 

 Novae, 1895, p. 64. Acanthocodium fragile Suringar, Algarum 

 Japonicaeum, Index praec. 1867, ihid., Hedwigia, vol. 7, 1868, p. 55; 

 Algae Japonicae, 1870, p. 23, pi. 8; ibid., Hedwigia, vol. 9, 1870, 

 p. 133. Codium mucronatum J. Agardh, Till. Alg. S^'st., 5th part, 

 1886, pp. 43, 44; Hurd, Pug. Sound Mar. Stat. Publ., 1916a, vol. 1, 

 pp. 109-135, pi. 19-24 ; Setchell and Gardner, Alg. N.W. Amer., 1903, 

 p. 232; Saunders, Alg. Harriman Exp., 1901, p. 416. Four Siphon. 

 Alg., 1899, p. 1, pi. 350, f. 1 a, b, c, d ; Collins, Green Alg. N. A., 1909, 

 p. 389; Collins, Holden and Setchell, Phyc. Bor.-Amer. (Exsicc), 

 no. 229. Codium tomentosum Tilden, Amer. Alg. (Exsicc), no. 281 

 (not of Staekhouse). 



The mucronate tip of the utricle of this plant is a prominent 

 specific character, but this character is subject to extreme variation. 

 J. Agardh (1886, pp. 43, 44) separated the species into three varieties 

 based chiefly upon the character of the mucro. We have studied and 

 compared plants from a considerable number of different localities 

 ranging from Alaska to Mexico, and have come to the conclusion that 

 the species cannot be split into varieties based upon that character. 

 Single plants may be found producing mucronate tips covering the 

 entire range of shapes, as regards thickening of the walls and acute- 

 ness of the tip, that have been used to designate the varieties. Miss 

 Hurd (1916o, p. 109) made a critical study of the species as occurring 



