1920] Setchell-Gm-dner : Chlorophyceue 263 



Growing on wood, rocks, and on other algae, in the lower littoral 

 belt. Alaska (Orea) to Mexico (La Paz). 



Linnaeus, Sp. Plant., vol. 2, 1753, p. 1163. Enteromorpha Linza 

 J. Agardh, Till Alg. Syst., part 3, 1883, p. 134, pi. 4, f . 110-112 ; Col- 

 lins, Green Alg. N. A., 1909, p. 206, Mar. Alg. Vancouver Is., 1913, 

 p. 102 ; Setchell and Gardner, Alg. N.W. Amer., 1903, p. 212 ; Howe, 

 Phyc. studies, V, 1911, p. 490; Collins, Holden and Setchell, Phyc. 

 Bor.-Amer. (Exsicc), no. 967 b; Tilden, Amer. Alg. (Exsicc), no. 

 384. "Viva Lactuca forma genuina" Tilden, Amer. Alg. (Exsicc), 

 no. 260 (not of Hauck). 



The figure of Dillenius (1741, pi. 9, f. 6) quoted by Linnaeus 

 (1753, p. 1163) under Ulva Linza, seems sufficiently characteristic to 

 distinguish this species. We find, however, that it becomes necessary 

 to include under the name a very considerable variety of forms. 

 Some of these forms are very narrow, while others are comparatively 

 broad. In some, the hollow stipe gradually expands into the blade, 

 while in others the passage from one to the other is extremely abrupt 

 and the blade is broad, even slightly cordate, at the base. Many 

 plants of Ulva Linza are short (a few cm. long) while some are very 

 long (up to 1 M. or more). The margins, in turn, may be perfectly 

 flat and plane while, in others, they are decidedly, even conspicuously, 

 undulate or deeply ruffled. The hollow stipe and greater or less extent 

 of hollow margin, however, distinguish all forms of Ulva Linza from 

 any other species of Ulva, and the considerable expanse of two-layered 

 blade distinguishes them from any species of Enteroviorpha. 



While Ulva Linza is an Enteromorpha at the base and on the lower 

 margins, it is decidedly an Ulva so far as the expanded blade is 

 concerned. It might, with justice, be placed in either genus, but 

 since the habit in general is that of an Ulva and the greater portion 

 of any plant of the species is ulvoid, it seems to us that the novice, 

 at least, is more likely to arrange it with Ulva than with Entero- 

 morpha. We have decided, therefore, to restore it to the genus Ulva. 

 It has been customary since the account of J. G. Agardh (1883, 

 p. 134) to distinguish two foiins of Ulva Linza, the one (f. lanceolata) 

 with the margins plane or undulate and the other (f. crispata) with 

 the margins crisped. Since all degrees of ruffling or absence of it 

 occur in plants seemingly to be referred to the species, it does not 

 seem practicable to distinguish sharply between them. 



