1920] Setchell-Gardner : Chlorophyceae 265 



even more closely, Kuetzing's figure of Phycoseris Linza (1856, pi. 16, 

 f . I ) , but is a smaller plant than that also. The short, flattened stipe 

 is solid. The narrow blade varies from plane to undulate or even 

 crisply ruffled on the margins. The cells are oblong or rounded in 

 section, each provided with more or less of a distinct wall. Although 

 we have only recently become acquainted with it, this seems to be a 

 vernal species. It has been observed in fertile condition in April. 



4. Ulva Lactuca L. 



Fronds short, usually broader than long, attached by a disk from 

 a broad or attenuate base, generally deeply and irregularly split, light 

 to dark green in color, delicate in texture, margins plane or ruffled; 

 membrane 35-50/* thick (usually about 40/*) ; cells in section nearly 

 square with rounded angles or slightly elongated, seldom one and one 

 half times higher than broad even in fertile condition. 



Growing attached at first in the upper littoral belt. From Alaska 

 (St. Michael) to Mexico (Gulf of California). 



Linnaeus, Sp. Plant., vol. 2, 1753, p. 1163 (in part?); Thuret, 

 Note Syn. Ulva Lactuca, 1854, p. 24; Thuret and Bornet, Etudes 

 Phyc, 1878, p. 5, pi. 2, 3 ; Collins, Green Alg. N. A., 1909, p. 214, 

 f. 75 (in part). Ulva Lactuca f. rigida Tilden, Amer. Alg. (Exsicc), 

 no. 386 (not of Le Jolis). 



Ulva Lactuca, as described by Linnaeus, is not so definitely delim- 

 ited as to be intelligible, so that different views have been held as 

 to its nature. A specimen exists in the Linnaean Herbarium (cf. 

 Benjamin Daydon Jackson, 1912, p. 147) labeled in the handwriting 

 of the younger Linnaeus. We have no knowledge of this specimen 

 and have seen no account as to its examination. It is certain that a 

 number of the earlier writers agree in referring here a plant which, 

 tubular at first, finally splits. On this account, the Ulva Lactuca L. 

 is a Monostronm or perhaps included both a Monostroma and an Ulva. 

 With all due respect to these authorities, it has seemed best to us to 

 follow a considerable number of recent writers who have followed the 

 opinion of Thuret (1854, p. 24) as to the real nature of Ulva Lactuca. 

 The plant described by Thuret and Bornet in their Etudes Phyco- 

 logiques (1878, p. 5, pi. 2, 3) is the one we have in mind in the refer- 

 ence of the specimens of our coast. This species has a frond broadly 

 lanceolate, attenuated to a very short stipe below, broadened and 

 more or less deeply and coarsely lobed above. The membrane is about 



