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I925 ] Setchell-Ganlner: MeUmophyceoi 551
solid when young, becoming more or less fistulose when old ; color dark
olive brown ; erect fronds annual, base perennial ; zoosporangia ellip-
soidal to obovoid, numerous, sessile on the parenchymatous cells or at
times lateral near the base of the paraphyses, 50-60^ long, 30-40/*
broad, paraphyses numerous, clavate, 70-85//. long, terminal cell much
enlarged, pyriform to spherical; gametangia very compact, covering
the whole surface of the ramuli, without paraphyses or hairs, pluri-
seriate, terminating in a 2-3-celled, sterile, usually clavate tip ; plants
dioecious.
Common on rocks in the middle and lower littoral belts. Ranging
from St. Lawrence Island in the Bering Sea to central California
(near Point Conception).
Setchell and Gardner, Phyc. Cont., VII, 1924, p. 6. Chordoma
abietina Ruprecht, MS. in Farlow, List Mar. Alg. U. S., 1876, p. 357;
J. Agardh, Till Alg. Syst., part 2, 1882, p. 74, pi. 3, figs. 2a, 2b;
Saunders, Alg. Harriman Exp., 1901, p. 424; Setchell and Gardner,
Alg. N.W. Amer., 1903, p. 251, pi. 18, figs. 16, 17 ; Collins, Holden
and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 281; Tilden, Amer. Alg.
(Exsicc), no. 348; Farlow, Anderson and Eaton, Alg. Exsicc. Amer.-
Bor., no. 94.
Heterochordaria abietina (Rupr.) S. and G. is one of the very fre-
quently occurring algae of western North America from Point Con-
ception in California northwards. It has two striking peculiarities,
viz., the possession of a well developed horizontal thallus from which
the erect fronds arise and also of the gametophyte of the same size as
the sporophyte. The horizontal thallus is often a fair sized and
reasonably conspicuous structure, at times several centimeters in
diameter, spreading at the periphery and consisting of overlapping
narrow, blunt and emarginate lobes. From certain appearances, it
seems possible that it may be perennial. In the sporophyte, the zoo-
sporangia seem to be confined to the ramuli, and this seems to be the
case also with the gametangia of the gametophyte which have not been
seen to occur on the main axis. J. G. Agardh (1882, p. 74, pi. 3, figs.
2a, 2b) has figured and described the gametangia and Okamura (1910,
p. 122, pi. 85, figs. 14. 15) has figured and described both the zoo-
sporangia and the gametangia. We have previously (1903, pp. 251,
252, pi. 18, figs. 16, 17) figured and described the horizontal thallus.