Ulva linza L.

1. Ulva Linza L. ; ' '
Plate 12. figs. 1-4
Frond lanceolate or linear-lanceolate, simple, 1-5 dm. long-. 1-20
cm. broad; stipe longer or shorter, hollow; upper part of the frond
flat, the two layers of cells completely united or remaining- free along
the whole or part, of the margins, which arc plane or more or less
undulate; membrane 25-70/* thick; cells usually vertically elongated
in section, up to twice as high as broad.
1920]
Setchell-Gardncr : Chlorophyceae
263
Growing on wood, rocks, and on other algae, in the lower littoral
belt. Alaska (Orca) to Mexico (La Paz).
Linnaeus, Sp. Plant., vol. 2, 1753, p. 1163. Enteromorpha Linza
J. Agardh. Till Alg\ Syst., part 3, 1883, p. 134, pi. 4, f. 110-112; Col-
lins, Green Alg. X. A., 1909, p. 206, Mar. Alg. Vancouver Is., 1913,
p. 102; Setchell and Gardner, Alg-. N.AV. Amer., 1903, p. 212; Howe,
Phyc. studies, V, 1911, p. 490; Collins, Holden and Setchell, Phyc.
Bor.-Amer. (Exsicc.), no. 967 b; Tilden, Amer. Alg. (Exsicc.), no.
384. “Viva Lactuca forma genuina” Tilden, Amer. Alg. (Exsicc.),
no. 260 (not of Ilauck).
The figure of Dillenius (1741, pi. 9, f. 6) quoted by Linnaeus
(1753, p. 1163) under Viva Lima, seems sufficiently characteristic to
distinguish this species. We find, however, that it becomes necessary
to include under the name a very considerable variety of forms.
Some of these forms are very narrow, while others are comparatively
broad. In some, the hollow stipe gradually expands into the blade,
while in others the passage from one to the other is extremely abrupt
and the blade is broad, even slightly cordate, at the base. Many
plants of Viva Linza are short (a few cm. long) while some are very
long (up to 1 M. or more). The margins, in turn, may be perfectly
flat, and plane while, in others, they are decidedly, even conspicuously,
undulate or deeply ruffled. The hollow stipe and greater or less extent
of hollow margin, however, distinguish all forms of Viva Linza from
any other species of Viva, and the considerable expanse of two-layered
blade distinguishes them from any species of Enteromorpha.
While Viva Linza is an Enteromorpha at the base and on the lower
marg-ins, it is decidedly an Viva so far as the expanded blade is
concerned. It might, with justice, be placed in either genus, but
since the habit in general is that of an Viva and the greater portion
of any plant of the species is ulvoid, it seems to us that the novice,
at least, is more likely to arrange it with Viva than with Entero-
morpha. We have decided, therefore, to restore it. to the genus Viva.
Tt has been customary since the account of J. G. Agardh (1883,
p. 134) to distinguish two forms of Viva Linza, the one (f. lanceolata)
with the margins plane or undulate and the other (f. crispata) with
the margins crisped. Since all degrees of ruffling or absence of it
occur in plants seemingly to be referred to the species, it does not
seem practicable to distinguish sharply between them.
NEW YORK
BOTANICAL
garden
PLATE 12
Ulva Lima L.
Fig. 1. A vertical section through the margin of a frond showing the separa-
tion of the two layers. Plant from Friday Harbor, Washington. X 250.
Fig. 2. A surface view of fig. 1. X 250.
Fig. 3. The same view as fig. 1. Plant from Admiralty Island, Alaska.
X 250.
Fig. 4. A surface view of fig. 3.
NEW YORK BOTANICAL GARDEN
02140080
02140080