T U te c o L m :.
P l a t e CCXLIII.
ULVA LACTUCA, Linn.
Ge n . Ch a e . Frond membranaceous, gre en, expanded, plane, (in some
cases saccate when yo u n g ,) composed of irreg u la r cellules. Fructification
; granules, often a rra n g ed in fours, s ca tte red over th e whole
fro n d . U lva ( Í . ) ,— supposed to b e from U l, water in Celtic.
U l v a lactuca; “ fro n d a t first obovate, saccate, in fla te d ,'a t le n g th cleft
down to th e b a s e ; th e segments plane, u n equal, laoimated, semitra
n s p a r e n t.” Grev.
Ulva lactuca. Urn. Sp. PL p. 1632. LigUf. M. Scot. p. 970. in part. Ag.
Sp. Alg. vol. i. p. 409. Ag. Syst. p. 189. Lyngh. Ilyd. Ban. p. 30. m part.
Grev. Crypt. s A t. 313. Grn. Alg. Brit. p. 172. Eook. Br. PL vol. ii.
p. 311. Harv. Man. p. 170.
H ab. On rocks, stones, shells, and the smaller algse between tide-marks.
Annual. May and June. Generally distributed round the Untisli
coasts, but less common than V. latissima.
G e o g k .D is tk . Shores of Europe.
U e sc k . Fronds tufted, from two to six inches high, at first forming an obovate
bao- closed at the summit, but soon bursting, and split quite to the base
into two or more segments which are often irregularly lobed or divided
the margin sometimes entire, but oftener jagged. Substance very thin and
delicate, semi-transparent, closely adhering to paper in drying. Colour a
peculiarly beautiful light yeUowish green. The surface glossy when dry.
Under the microscope the frond is seen to consist of closely packed, quaternate
cells, lying in a transparent membrane.
To Dr. Greville belongs the merit, as far as British naturalists
are concerned, of having first clearly pointed out the characters
by which this delicate plant may be distinguished from the more
common U. latissima, and therefore I have thought it best to
preserve the diagnosis given by that author in his Algæ Britan-
nicæ. The eharacters are most obvious in an early stage of
growth, when the present plant forms an obovate sac, not very
unlike a greatly distended Enteromorpha; while U. latissima is
at all periods of its growth a flat membrane. Other characters
are found in the substance and colour. U. lactuca is of a brighter
and yellower green, and more glossy when dry ; and its substance
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