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1925] SetcheU-Gardner: Melanophyceae 709
1. Cystoseira osmundacea (Menz.) Ag.
Fronds robust, perennial, up to 6 m. long ;
stipe nearly triangular
in cross-section, somewhat geniculate, having numerous prominent
scars caused by the disintegration of the primary branches; flattened
portion in the lower part of the primary branches with deep rounded
sinuses and prominent pinnae, rounded at the outer ends, very closely
resembling the fronds of certain ferns, gradually reduced in size
toward the outer end of the rhachis and finally merging into the long,
branched, filiform branches; vesicles 5-12 seriate, 4-6 mm. diam.,
mostly in the branches having only the receptacular ramuli beyond;
receptacles conspicuous, abundant, often much branched, terminating
the ramuli ;
plants dioecious.
Growing in tide pools in the lower littoral belt and in the upper
sublittoral belt, usually in moderately sheltered localities.
Central Oregon (Coos Bay) to Lower California (Ensenada).
Agardh, Sp. I, 1820, p. 69 ; Gardner, New Fucaceae, 1913, p. 333.
Fucus osmundaceus Menzies, in Turner, Hist. Fuc, vol. 2, 1809, p. 92,
pi. 105.
The type locality of the species is Port Trinidad, Humboldt County,
California. Two forms, fairly constant in structure, have been noted
as follows
:
Cystoseira osmundacea f . typica Gardner
This form comprises the shorter specimens, more robust throughout,
usually with fewer (5-8) vesicles in a series. It grows, as a rule, in
more exposed localities in tide pools along low-tide level, and seems to
be limited largely to the central and northern parts of the range.
Gardner, New Fucaceae, 1913, p. 335, pis. 51, 52.
Cystoseira osmundacea f. expansa (Ag.) Setchell
Forma expansa includes the more delicate and slender, much
elongated (up to 6 m. long) specimens with smaller vesicles and a
larger number (7-12) in a series. It is most luxuriant in the southern
part of the range.
Setchell, in Collins, Holden and Setchell, Phyc. Bor.-Amer.
(Exsicc), no. XLVIII ; Gardner, New Fucaceae, 1913, p. 336, pi. 53.
Cystoseira expansa Agardh, Syst. Alg., 1824, p. 290. Cystoseira
osmundacea Collins, Holden and Setchell, Joe. rib., nos. XCVI and
CXV a, not b. Both distributions are small parts of plants.