1925] Setchcll-Gardncr: M rhino phyceae 715 



Eu sargassum. They are not regularly two-edged and serrate-dentate 

 along the margins. Many of them are slightly flattened above, some- 

 what spinose, and crowned with a leaf rudiment. The species fits into 

 this section better than into any other. 



6. Sargassum horridum S. and G. 



Basal parts unknown; branches and branchlets muricate, leaves 

 linear-lanceolate, acute, midrib percurrent, margins deeply and doubly 

 serrate ; cryptostomata numerous and conspicuous on the leaves, stems, 

 and vesicles ; vesicles sparse, occupying the position of leaves near the 

 base of the ramuli or scattered among the receptacles, spherical, 

 4-8 mm. diam., short-petiolate ; receptacles decompoundly ramose, 

 decidedly spinose. 



Cast ashore, La Paz, Lower California. 



Setchell and Gardner, Mar. Alg., Gulf Calif., 1924, p. 734, pi. 20, 

 figs. 65, 66. 



Like the majority of our specimens from the Gulf of California, 

 the specimens of this species have neither holdfast nor stipe. Pre- 

 sumably many of them grow only in the sublittoral belt and collectors 

 have observed only such specimens as have been cast ashore, and these 

 are usually fragmentary. Otherwise the specimens of 8. horridum are 

 in excellent condition. 



7. Sargassum Marchantae S. and G. 



Basal parts unknown; primary branches 4.5-6 dm. high, terete, 

 smooth; secondary branches numerous, densely fructiferous; leaves 

 4-6 cm. long, 3-5 mm. wide, linear-lanceolate, acute, midrib percurrent, 

 margins irregularly serrate-dentate ; cryptostomata numerous and con- 

 spicuous ; vesicles sparse, spherical, on short pedicels near the base of 

 the ramuli or near the base of the branching receptacles, 4-6.5 mm. 

 diam., smooth; receptacle several times forked, occasionally one fork 

 developing into a leaf or a vesicle forming a "heteroclyte cyme ( ?)," 

 but all others fructiferous and from a single pedicel, supported near 

 the base of a leaf, cylindrical, blunt, spinulose, the whole cyme 10-15 

 mm. long. 



Cast ashore, Eureka, near La Paz, Lower California. 



Setchell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 735, pi. 19, 

 fig. 63. 



Sargassum Marchantae is probably closely related to 8. Lieumanni 

 J. Ag. 



