NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 237 



coasts. Hitherto, San Diego, California, had marked the southern limits 

 of this cold-water genus, and to find two species in the Gulf of California 

 is indeed unexpected. The waters of Puerto Refugio at 15 fathoms' depth, 

 however, are quite as cold in March and earlier as some of our more 

 northern Pacific waters, 13-14°C., and therefore allow environments 

 acceptable to the members of this genus. The presence of Desmarestia, 

 on the other hand, does not seem in accord with the complete absence of 

 members of the Laminariales. Yet, considering the poorly explored nature 

 of the sublittoral waters of the Gulf, some even of these may remain to 

 be found as more extensive exploration is carried out. 



Family Laminariaceae 



Genus MAGROCYSTIS C. Agardh 

 Macrocystis pyrifera (Turner) Ag. 



C. Agardh, 1820, p. 47; Setch. & Gard., 1924, p. 728. 



J. 78, caught in the log line of vessel between Espiritu Santo Island 

 and La Paz, April. 



"A single specimen about 3 feet long was brought aboard the ship, but 

 no specimens were found growing attached within the Gulf" — Johnston. 



Family Sargassaceae 

 Genus SARGASSUM C. Agardh 



J. Agardh, 1889, pp. 32-34; Setch. & Gard., 1925, p. 711 ; Setchell, 1937, 

 pp. 127-158. 



The Sargassa of the Gulf of California, as determined from a study 

 of almost every specimen known to have been collected in that area, may 

 be arranged under four major type-groups according to leaf-shape, cos- 

 tation of the leaf, and cryptostomata. These characters mark off groups 

 of species with reasonable distinctness, and, with few exceptions, these 

 groups seem to be natural, the members of each showing close mutual re- 

 lationship. 



All of the Sargassa of the Gulf fall under J. G. Agardh's subgenus 

 Eusargassum. Further arrangement according to his system, that is, under 

 his groups Zygocarpicae, Acanthocarpicae, Malacocarpicae, etc., is too 

 confusing to be attempted, since when the sexuality of the various species 

 is taken into consideration the characters used as a basis for Agardh's 

 broader classifications are too unreliable. Therefore, in this paper, the 



