NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 199 



characteristic and conspicuous elements are worthy of mention for com- 

 parison with the floras farther north. Two species are prevalent and 

 especially conspicuous: Sargassum sinicola and Padina Durvillaei. This 

 Sargassu?n is here and in other localities accompanied by one or several 

 other less abundant species. Padina Durvillaei, however, is the only mem- 

 ber of the genus anywhere abundant in our region. It is apparently a 

 common plant south along the Mexican coast all the way to Central 

 America. In the Gulf it occurs at all the northern stations, often in great 

 abundance. Tropical elements such as were found at San Gabriel Bay 

 are absent or very obscure. Codium simidans and Gracilaria compressa 

 are occasional. Small rock-cover species begin to be conspicuous in this 

 region but do not reach the rich development of those of the island reefs 

 to the north. 



The first rich winter vegetation is encountered on the south shores 

 of the islands of the large northern group. All of the prevalent plants 

 of the Guaymas area are present and many others in addition. Colpo- 

 menia, Gigartina, Gelidium, Gracilaria, Hypnea, Laurencia, Lomen- 

 taria, Centroceras are common fleshy genera. The articulated corallines, 

 Corallina and Amphiroa, are abundant and form, with various crus- 

 taceous Lithophyllum species, dense covers over shore rocks. A list of 

 species collected at Turner's Island is given on p. 357. 



Having been acquainted with the flora of the coast of California, the 

 author was struck with the peculiar appearance of this vegetation. The 

 entire aspect is at variance with floras a few hundred miles northwest on 

 the California coast. The most obvious differences are in regard to the 

 "Kelps." The Laminariales are not represented in any part of the Gulf 

 of California. These plants, so conspicuous and important a part of the 

 California marine flora, are utterly lacking from these shores as are most 

 of the other larger brown algae. The order Fucales is represented only 

 by Sargassum, which is, however, the dominant brown alga of the Gulf. 

 Other fucoids such as Fucus, Pelvetia, HalidrySj and Cystoseira, so com- 

 monplace to Californians, apparently do not occur. 



It is well known that the larger brown algae, particularly the Lami- 

 nariales, are characteristic of cool or cold waters, rarely extending into 

 warm seas. On the outer coast of Lower California there is evidence of 

 their extension perhaps as far south as Magdalena Bay, where rising sum- 

 mer temperatures undoubtedly become limiting for the development of 

 critical phases in the life cycle. In the Gulf of California temperature 

 conditions during the winter season are in general quite in accord with 



