NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 247 



Stones (pi. 35, fig. 9). The plants lacked any form of rhizome; and the 

 lower parts of the stems were rough, thick, and gnarled, the upper parts 

 mostly muricate. No mature specimens were present. 



At Turner's Island the dark Sargassum Camouii was not found ; in- 

 deed, only very young Sargassum plants were present. Some of these 

 proved to be immature plants of S. sinicola (a species collected at the same 

 station in January). These showed stiff tangles of short rhizomes as basal 

 holdfasts (pi. 35, fig. 10). 



Speculation in regard to the Sargassum sinicola problem in this region 

 suggested that, since young plants are present in midsummer, old floating 

 plants being cast up at the same time, and mature, attached plants in Jan- 

 uaiy, at least in this particular locality a marked seasonal development of 

 this species occurs. 



On the south shore of Tiburon Island, Sargassum Camouii was found 

 nearly mature in both January and July. This species, then, has different 

 seasonal development from that of S. sinicola] and the observation sug- 

 gests that, when more extensive field investigations can be made, the sea- 

 sonal development may prove specifically distinctive in these species and 

 in others as well. 



Sargassum horridum S. & G. 



Plate 38, Figs. 1-4 



Setch. & Gard., 1924, p. 734, pi. 20, figs. 65, 66. Sargassum Marchantae 

 S. &G., 1924, p. 735, pi. 19, fig. 63. 



Basal parts unknown; branches and branchlets muricate in oogonial 

 plants, smooth and terete in antheridial plants; leaves linear-lanceolate, 

 acute, midrib percurrent, margins irregularly serrate-dentate to doubly 

 serrate ; cryptostomata numerous and conspicuous ; vesicles spherical, 4-8 

 mm. in diam., short-pedicellate ; receptacles sexually dimorphic ; oogonial 

 decompoundly ramose, decidedly spinose; antheridial less abundantly 

 branched, more slender, merely finely spinulose. 



M. 17, 22, Eureka, Lower California. 



Bryant 7, from the islands of San Jose and Espiritu Santo, and J. 77, 

 from between Ceralbo and Espiritu Santo Island, April, are sterile but 

 seem to belong here. 



Sargassum sinicola S. & G. 



Plate 35, Fig. 10; Plate 38, Figs. 5-11; Plate 39, Figs. 1-11 



Setch. & Gard., 1924, p. 736, pi. 20, fig. 73. Sargassum cylindrocarpum 

 S. & G., 1924, p. 738, pi. 21, fig. 77. Sargassum polyacanthum f. 



