1920] Setchell-Gardncr : Chlorophyceae 251 



4. Enteromorpha compressa (L.) Grev. 



Plate 14, figs. 7, 8 ; plate 16, fig. 3 



Frond tubular, more or less compressed, sometimes constricted, 

 varjnng much in dimensions; branches usually simple, cylindrical or 

 expanding above, in either case narrowed at the base, similar in appear- 

 ance to the main axis ; cells in no definite order ; membrane rather thin. 



Growing in the middle and lower littoral belts. From Alaska 

 (Bering Sea) to Mexico (Magdalena Bay), 



Greville, Alg. Brit., 1830, p. 180, pi. 18 ; Collins, Green Alg. N. A., 

 1909, p. 201, IVIar. Alg. Vancouver Is., 1913, p. 101; Setchell and 

 Gardner, Alg. N. W. Amer., 1903, p. 213. Enteromorpha proUfcra 

 Setchell and Gardner, Alg. N.W. Amer., 1903, p. 221 (as to no. 5687 

 only). Enteromorpha fascia Postels and Ruprecht, Illust. Alg., 1840, 

 p. 21 ; Setchell and Gardner, Alg. N.W. Amer., 1903, p. 211 ; Collins, 

 Green Alg. N. A., 1909, p. 204. Viva compressa Linnaeus, Fl. Suec, 

 Ed. II, 1755, p. 433. 



We have followed the opinion of J. G. Agardh (1883, p. 137) as 

 to the nature and limits of Enteromorpha compressa. The habit of 

 typical plants is well illustrated in our figures (plate 14, figs. 7, 8, and 

 plate 16, fig. 3) . The branches may arise from the very base or at differ- 

 ent heights along the axis. They are uniformly constricted at the base 

 and usually expanded to a rounded tip. The broader portions of the 

 frond are almost always flattened and the layers may be very imper- 

 fecth' separated. Sections of such imperfectly tubular fronds often 

 bear a striking resemblance to those of Ulva Lima, especially when 

 separation is present only on the margins as may happen in spots. 



The differences between Enteromorpha compressa and E. minima 

 have already been noticed under the latter species. The resemblance 

 to nai-row forms of Ulva Lima is sometimes puzzling, especially in 

 unbranched specimens (var. suhsimplex J. Ag.) or in specimens only 

 slightly branched. 



We refer under Enteromorpha compressa tlic E. fascia of Postels 

 and Ruprecht (1840, p. 21) since the habit (plate 16, fig. 3) is the 

 same and the size and shape of the cells, both in surface view and in 

 cross section, are identical. The cell contents, however, in the type 

 specimens of E. fascia are disorganized in such a way as to seem 

 almost as if there were groups of small cells within the larger ones. 

 The color of the type specimens is also somewhat brownish. We 

 ascribe this as well as the peculiar appearance of the cell contents to 



