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1925 1 Setchell-Gardner: Melanophyceae 613
45. Thalassiophyllum Post, and Rupr.
Holdfast of stout, dichotomously branched hapteres; primitive
stipe short, not elongating but thickening, soon buried among the stout
hapteres; blade soon eroded to the base and developing two lateral
scrolls which unroll as they develop from thickened margins and form
fan-shaped, spirally twisted, closely and regularly perforated, partial
blades; numerous secondary stipes or branches, arising along the
thickened margins, bearing small blades; no mucilage ducts in either
the stipe or blade ; sori in irregular dark brown areas ; plants perennial.
Postels and Ruprecht, Illus. Alg., 1840, p. 11.
There are two peculiarities of the genus Thalassiophyllum, viz.,
the one-sided fan-shaped blades unrolling from a one-sided scroll,
borne on what seems to be a branched, heavy, solid stipe. From the
development (cf. Setchell, 1905a, p. 123, pi. 13, figs. 6-13) it appears
that the early stages resemble those of Agarum in being bilaterally
symmetrical, with basal margins inrolled. By the disintegration of
the central portion of the blade, the basal margins only are left with
their scrolls. One margin ceases to develop, as does the short primi-
tive stipe. The other basal margin thickens, elongates, and becomes
stipe-like, bearing its one-sided blade. The branches (false) arise
(cf. Rosenthal, 1890, Flora, vol. 73, pp. 140, 141, pi. 8, figs. 33, 34) by
adventitious outgrowths from the developing scroll-like base of the
blade. The branching of Thalassiophyllum is a pseudo-branching and
of a pseudo stipe not to be confounded with that of the Lessoniaceae
or in Egregia of the Alariaceae.
Thalassiophyllum Clathrus (Gmel.) Post, and Rupr.
Plate 72
Plants 12-15 dm. high, rigid; holdfast and stipe as in the genus;
blade thick and coriaceous, with the numerous, large elliptical per-
forations with roughened margins radially arranged; color dark
brown to deep olive green, much darker toward the basal portions.
Growing on rocks in the sublittoral belt. Bering Sea to the Straits
of Juan de Fuca (the last mentioned locality fide MacMillan, 1902,
p. 219).
Postels and Ruprecht, Illus. Alg., 1840, p. 11, pis. 18-19; Setchell,
Alg. Prib. Isl., 1899, p. 592, Post-emb. Stages, 1905a, p. 123, pi. 13,