Ulva expansa (Setch.) Setch. & N.L.Gardner

BOTANICAL
GARDEN
Ulya expansa (Setchell) Setchell & Gardner,comb.nov.
Uni v, Cai if. Pubi. Bo t. 7 : IX. 284. 8 J1 1920.
Frond ample, pale green, orbicular or broadly
elongated, margin deeply ruffled; frond 60-70 |i thick
in the middle, 38-45 jx on the margins; cells, m sect-
ion, vertically elongated in the middle of the frond
(up to 28-30 jx long, 10-12 wide), nearly square in
the margins.
Growing on rocks in the lower littoral belt.
Puget Sound, Washington, to Mexico (La Paz).
Ulva fasciata f. expansa Setchell, in Collins,
Holden and Setchell, Phyc.Bor.-Amer.(Bxsicc. ), no.
LXXVII; Collins, Green,Alg. N. A., 1909, p. 216.
We find along the coast of central California a
broad species of Ulva, often also long, something like
Ulva latissima in appearance, yet of a more vivid green
color, thicker in the center of the frond and with dis-
tinct, broad, ruffled margins. The cells of the thick-
er center of the frond are distinctly palisade-like in
section, while on the thinner margins they are nearly
square. A younger specimen of this plant was distribut-
ed by one of us as Ulva fasciata f. expansa (Phyc. Bor.-
Amer.,no* LXXVII), but it has seemed, on further study,
to belong neither to Ulva fasciata Belile nor to the
Ulva fasciata f. taeniata also distributed by one of us
(Phyc. Bor.-Amer., no. 809), but described later on in
this account as Ulva taeniata. We, therefore, describe
it as an independent species under the name of Ulva ex-
pansa.
Ulva expansa, so far as we have observed it, re-
mains attached only for a short time. It soon becomes
free and floats or drifts, increasing in size, becoming
at times at least 3 M. long and varying in width from
18 cm. to 75 cm. In form and structure it differs from
Ulva latissima and from all the other species of Ulva of
our coasts. It comes nearest to Ulva fenestrata, as we
have desoribed that speoies, but is little, if at all,
perforate. Plants of what appears to be the same species
have been found in the Puget Sound region and Howe (1911,
p. 490) is inclined to credit here some from La Paz,
Mexico.
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