2(0 University of California Publications in Botany [Vol.8 



Agardli, Sp., vol. 1, part 2, 1822, p. 410. UlvO' Lactuca var. rigida 

 Le Jolis, Alg. Mar. Cherb., 1863, p. 38; Collins, Green Alg. N. A., 

 1909, p. 215 (in part), Mar. AJg. Vancouver Is., 1913, p. 103 (in 

 part) ; Saunders, Alg. Harriman Exp., 1901. p. 410 (in part) ; 

 Setchell and Gardner, Alg. N.W. Amer., 1903, p. 209 (in part) ; Howe, 

 Phyc. Studies, V, 1911, p. 490. 



Ulva rigida must needs be carefully studied and redescribed from 

 the type specimen before any exact knowledge is possible as to the 

 nature of the species. Agardh (1822, p. 410) describes it as from 

 3 or 4 up to about 9 inches long, split to the base into curved and crisp 

 laciniae. J. G. Agardh (1883, p. 168) describes it as having cells 

 vertically elongated in section to 2 to 3 times their width. He, how- 

 ever, refers as typical the figure of Ulva Lactnca of Thuret and Bor- 

 net's Etudes Phycologiques (1878, pi. 2, e). Yendo (1916, p. 244) 

 says that J. G. Agardli has taken a broader view of the species than 

 did C. Agardh. Yendo refers to U. rigida, in the sense of its founder, 

 the Ulva conglohata Kjellm. and its f. densa as well as the Ulva fasci- 

 ata f. caespitosa Setchell (Phyc. Bor.-Amer., no. 809). Yendo does 

 not, however, state definitely just the characters of the type of U. 

 rigida Ag. 



The Ulva conglohata' Kjellm. seems to us to agree well with the 

 U. fasciata f. caespitosa Setchell (Phyc. Bor.-Amer., no. 809, nom. 

 nud.), both as to habit and as to structure. The cells in each are only 

 slightly, if at all, elongated vertically in section. We are inclined to 

 refer both of these plants to Ulva Lactnca as small forms. The Ulva 

 conglohata f. densa, however, seems different in its structure. Judg- 

 ing b}^ Kjellman's figure (1897a, pi. 3, f. 15), the cells are decidedly 

 vertically elongated in cross section, and this form probably, therefore, 

 belongs to U. rigida in the sense of J. G. Agardh. 



We have, in the light of what has been written, considered the 

 Ulva rigida to be a low plant, rigid, deeply divided, rather thick and 

 with cells vertically elongated in section. The membrane usually 

 shows a rather thick hyaline layer under each surface, and another 

 between the layers of cells. We have found that certain of our speci- 

 mens conform to these characters and are to be distinguished by them 

 from any other species of Ulva. 



