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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.
fig. 63.
J. Ag.
Cast ashore, Eureka, near La Paz, Lower California.
Setchell and Gardner, Mar. Alg. Gulf Calif., 1924, p. 735, pi. 19,
Sargassum Marchantae is probably closely related to 8. Lieumanni