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192.")] Setchell-Gardncr: Melanophyceae 707
Lepidium Ruprecht, Tange Ochot. Meeres, 1851, p. 347; Collins,
Holden and Setchell, Phyc. Bor.-Amer. (Exsicc), no. XLVII. Cysto-
seira geminata Agardh, Syst. Alg., 1824, p. 286.
Since publishing our account in the Algae of Northwestern
America, we have not been able to secure any additional data by which
to separate the four species of the genus Cystophyllum, accredited to
our region and which we united into one species under the foregoing
combination.
71. Halidrys Lyngb.
Plants consisting of a solid holdfast, a stipe, flattened and terete
fronds ; the flattened fronds alternate on the stipe, these metamorphos-
ing into pinnately branched filiform branchlets; cysts in a series,
developing in the flattened fronds, leaving a margin on either side of
the series ; these fronds terminating in branched receptacles ; one egg
cell in each oogonium ; monoecious or dioecious ; perennial, the fruiting
fronds dying back to the stipe each year.
Lyngbye, Hydrophyt. Dan., 1819, p. 37.
But two species of this genus, as restricted by Greville (Alg. Brit.,
1830, p. xxxiv), are at present known, H. siliquosa (L.) Lyngbye, on
the Atlantic coast of Europe, and the following species on the coast
of southern California.
Halidrys dioica Gardner
Stipe arising from a flattened, solid, warted base, terete, bent at the
"nodes," 40-50 cm. long, 4-6 mm. diam., solid, flexible, not forked;
primary pinnae annual, arranged alternately upon the stipe, always
arising just below the growing point, 10-18 dm. long, flat and linear
at the base, pinnately branched above, the linear portion 10-25 cm.
long, 8-12 mm. wide ; secondary branches or pinnules sessile, flat, acute
or obtuse at the apex, the oldest ones entire, the younger ones variously
notched and incised, the incisions increasing in depth, and the seg-
ments increasing in length toward the apex of the branch, the upper-
most becoming pinnately branched; the upper secondary branches
develop flattened, margined, lanceolate, acuminate, short pediceled air
vesicles, divided into 5-9 chambers, slightly constricted at the divi-
sions, the oldest rounded at the base and mucronate at the apex ;
apex of the younger ones developing farther into branched filiform
receptacles and these in turn bearing many conceptacles ;
the
plants peren-