230 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



lected in June, are 8 to 12 cm. high and with broad segments (5-8 mm.). 

 In February, 1940, the author found specimens cast up in abundance on 

 the beach near San Jose del Cabo. They are up to 16 cm. high and with 

 only a few broad segments from the basal parts, the upper parts being 

 very abundantly branched into narrow segments about 1 mm. in width. 

 So little do the upper parts of these plants resemble the more typical broad 

 segments of A'^. zonarioides that they were at first suspected of being of a 

 different species. A careful examination of the lower parts and younger 

 segments showed convincingly, however, that the plants should be placed 

 here. They have woody, stupose axial parts and are apparently over- 

 mature. 



Poindexter has recently collected at Punta Pefiasco, Sonora, March, 

 1941, several specimens which correspond closely with Johnston's Tor- 

 tuga Island material. 



Genus PADINA Adanson 

 Padina Durvillaei Bory 



Bory, 1826, pi. 21, fig. 1 ; Setch. & Gard., 1924, p. 729. 



The numerous collections of this species by Marchant, Brandegee, 

 Bryant, and Johnston (S. & G. loc. cit.) showed that it is abundant and 

 widely distributed in the lower littoral and upper sublittoral belts 

 throughout the Gulf of California during the months April to June. The 

 present collections (which include specimens obtained in November, De- 

 cember, January, February, March, April, and July) allow us to con- 

 clude that this plant is perennial in the Gulf and is adaptable to great 

 variations of water tempei'ature known to exist in its habitats. 



The species is to be found at almost all shore stations, but grows 

 most abundantly in large colonies on the smooth rock and sand bottoms of 

 shallow bays and lagoons. E. F. Ricketts, Pacific Biological Laboratories, 

 Pacific Grove, California, makes the following statement of observations 

 at Puerto Refugio, April 2, 1940: "Very common flat alga; acres of the 

 littoral were choked with this form." 



Development of new fronds from the perennial bases apparently be- 

 gins in late fall and becomes most rapid by about December. January and 

 February collections are of maturing specimens, mostly with fresh, full, 

 nonlacerated margins. Collections from late July to early November are 

 largely lacerated and covered with other organisms, and are obviously 

 old. Some early December collections show many very young fronds, no 

 old ones. Specimens collected near Guaymas, December 22, show great 

 increase in growth over those collected three weeks earlier. 



