i
Root a very minute disk. Fronds aggregated or solitary, one to
two feet long, two or three inches wide, narrow at the base (except
when the attachment is central, which sometimes happens), but expanding
immediately into an ovate, ovate-linear, or nearly linear frond,
waved at the margin. Fructification ; I. minute quaternate granules
covering the whole surface; 2. irregular scattered sori of larger ovate
granules, mostly situate towards the base. Substance very thin, and
membranous, but somewhat tenacious. Colour pui-ple, acquiring a
violet tint in the dried state.
A more beautiful species than the ])receding one, somewhat brighter,
and more transparent. I have not observed the sori, which are therefore
given on the authority of Agardh, who speaks of the ovate granules
composing them as three times larger than the quaternate granules.
The latter are about half the size of the quaternate granules
of Porphyra laciniata. Although in its ordinary state this species is
about twelve or sixteen inches in length, it sometimes attains a much
larger size. I have seen a specimen found by my friend Dr Hasel,
which measured not less than tiiree feet and a half. The margin of
the frond is very thin, and sometimes so slightly waved as to appear
almost flat.
3. P o r p h y r a l in e a r i s . Tab. XV III,
Frond lineal- or linear-lanceolate acute, the margin nearly flat.
Viva purpureay v a r . elongata, L y n g b . H y d ro p h . D a n . p . 20.
H a b . On rocks and stones within high water-maik. Annual. April
and May. Rocks beneath Peakhead, near Sidmouth, abundantly.
Root a very minute disk. Fronds aggregated, three to five inches
in length, two to three lines in width, linear or linear-lanceolate, acute,
always rising with a distinct, though exceedingly short stem, the margin
very slightly waved. Fructification, oval granules, not arranged
in a quaternate manner, but partly scattered and partly in lines.
Substance thin, very tender and flaccid. Colour a reddish purple.
A beautiful and singularly neat-looking little plant, and uniformly
constant in its form. The rocks, at the only spot where I observed it,
were rendered purple hy its delicate fronds. The different arrangement
of the granules preclude its being regarded as a miniature state
of either of the preceding species; at the same time, I believe it to be
the plant described by Lyngbye as a variety of his Ulva purpurea,
which is of a lanceolate form, scarcely a span long, half an inch wide, and
found growing at high water-mark on the rocks of the Faroe Islands.
G e n u s X LV III. ULVA, Linn. Tab. X V III.
G e n . C h a r . Frond nicmbvaiiaccous, of a green colour, plane
(in some cases saccate and inflated in the young state).
Fructification, minute granules mostly arranged in fours.
O bs. The word Ulva seems to have been in common use at an
early period, and occurs frequently in the Latin poets, but in so vague
and indefinite a sense, that it would apply to any or to all marsh-
plants. It is said by De Théis to be derived from the Celtic id,
water ; and it is therefore highly probable that, in its original sense, it
was a general designation for aquatic vegetables. Linnæus is considered
as the first botanical authority for the genus, but so little was
known about these plants in the time of our great master, that some
of his Ulvæ have suffered the same fate as many of his Fuci and
Confervæ. <•
The Ulvæ, aS' at present defined, are of very general distribution.
Species occur in salt and fresh water, and on the surface of damp
ground, the shaded roofs of old thatch-covered buildings, and even on
walls and stones, Some do not exceed a line, others are not less than
one or two feet in length.
* Species confined to the sea.
1. U lva l a t is s im a .
Frond plane widely oblong or roundish waved of a full green colour
and very tender substance.
Viva latissima, L in n . F I . S u e c . p . 433. Ag . S p . A lg . v . 1. p . 407. S y s t. A lg . p . 180,
Viva Lactuca, S m . E n g . B o t. t . 1551. G r e v . F I. E d in . p . 299.
Viva Lactuca, v a r . latissima, L ig h t f . F î . S c o t. p . 9 7L
H a b . Attached to rocks, stones, shells, &C. in the sea, very com^
mon. Annual, Summer and autnmn.
*