1920] Setcheil-Gardner : Chlorophyceae 239 



In the sublittoral belt, growing on Zostera. Known definitely only 

 from the waters of the Puget Sound region. 



"Monostroma zostericolum" Tilden, Amer. Alg. (Exsicc), no. 388, 

 1900. Monostroma leptodermum Collins, Green Alg. N. A., 1909, 

 p. 213; Setehell and Gardner, Alg. N.W. Amer., 1903, p. 209 (prob- 

 ably not of Kjellman). 



Monostroma zostericola is known thus far from the original collec- 

 tion by Tilden from the waters between Brown and San Juan Islands, 

 Washington ; from Port Renfrew, Vancouver Island, British Colum- 

 bia, collected by Butler and Policy (cf. Collins, 1913, p. 103, under 

 M. leptodermum) ; and from near Victoria, British Columbia, collected 

 by one of us (Gardner). There is some reason for referring here, 

 although doubtfully, young specimens from Monterey previously 

 placed, under M. Grevillei. The specimens of all collections agree in 

 showing sessile plants, attached and split in such a way as to suggest 

 their earlier saccate form and growing on Zostera. The species is 

 very delicate and its membrane very thin. The only species of this 

 genus on our coast with anything like so thin a membrane is our 

 Monostroma areolatum, which differs decidedly' in size, undulate and 

 crisped lobes, areolate surface and cells in definitely delimited and 

 separated groups. Collins, in various papers, has been inclined to 

 refer the Tilden plant to 3Ionostro'ma leptodermum, of Kjellman 

 (1877fl, p. 52, f. 23, 24). Kjellman 's plants, unfortunately, were not 

 found attached, but were floating fragments, the largest of which was 

 10 cm. long and about 6 cm. wide. We have seen no entire plants 

 among the considerable number examined from our coast which 

 approach these dimensions. Kjellman also states that his larger frag- 

 ment had the margins undulate and crisped which is not the case in 

 any of the specimens from our coast. The cells in ours seem to agree 

 fairl}^ well with the description and figures of Kjellman except in 

 being more elongated vertically than horizontally in cross section. 



Rosenvinge (1893, p. 944, f. 49, 1894, p. 148, f. 49) and Jonsson 

 (1904, p. 63) refer a very different plant from ours to the Monostroma 

 leptodermum Kjellm. Their plant has a long, slender, tubular stipe 

 and the membrane is undulate and ruffled. It seems best to us, there- 

 fore, to consider that their plant is more likely to represent Kjellman 's 

 species and to place ours under the name bestowed upon it by Tilden. 



