Ulva dichotoma, H u d s . S m . E n g . B o t. t . 774. L y n g b . H y d r o p h . D a n . p . 31. t . 6.
V a r . /3 intricata. F r o n d v e r y n a r r o w , m u c h b r a n c h e d , tw is te d a n d e n ta n g le d .
Zonaria dichotoma, v a r . intricata, Ag . S p . A lg . v . 1. p . 134. S y s t . A lg . p . 266.
H a b . In the sea, parasitic upon various AlgcB. Annual. Summer.
Common on most parts of the British coast. Var. g, on the Dumfriesshire
coast. Dr Richardson.
Root a small mass of filaments. Fronds several from the same base,
three to twelve inches in length, one to four lines in width, divided
from the very bottom, many times dichotomous, the margins quite entire.
Fructification, on some plants ovate, solitary, scattered, blackish
seeds; on others, seeds collected into little dense scattered roundish
clusters; both kinds bursting through the epidermis, and becoming at
length prominent. Substance thin and membranaceous, adhering to
paper when dry. Colour yellowish-green.
To Mrs Griffiths I am indebted for beautiful specimens, covered
with the scattered single seeds, first observed, I believe, by herself.
On other specimens, communicated by the same lady, are numerous
minute vesicles on both sides of the frond, similar, I presume, to those
alluded to in “ English Botany.” They do not appear to be at all
connected with the fructification, though, when in a young state, the
seeds sometimes happen to be included by them. When the seeds
are collected into little sori or spots, they are densely wedged together,
and are fixed by the lower extremity of their pellucid case.
2. D ic t y o t a a t o m a r ia .
Frond membranaceous, between palmate and flabelliform, irregularly
cleft and laciniate, seeds forming waved transverse lines, with others
scattered in the intervals.
Dictyota zonata, L am o u r E s s a i, p . 57.
Dictyota ciliata, L am o u r . E s s a i , p . 58.
Zonaria atomaria, A g . S p . A lg . v . 1. p . 128. S y s t . A lg . p . 264. G r e v . FI. E d in . p . 298.
S p r e n g . S p . P I . v . 4 . p . 327.
Ulva atomaria, W o o dw . S m . E n g . B o t . t . 419.
H a b . In the sea, on rocks. Annual. Summer. On the shore at
Cromer, Mr Wigg. At Corton and Gunton, Mrs Fowler. In the
pools among the rocks, about the Worm’s Head, in Glamorganshire,
Dillwyn. In pools among the rocks at Sidmouth, Torquay and Ilfra-
comb, Mrs Griffiths. Frith of Forth, cast on the beach, exceedingly
rare.
Root a mass of woolly filaments. Fronds several from the same
base, four to ten inches long, the general outline either flabelliform or
wedge-shaped, three to nine inches in width, divided very deeply in a
somewhat palmate manner, into a few large segments, which are also
variously cleft to about half way down into smaller ones, and these
again often laciniated and cut at the extremity, the mai-gins often more
or less ciliated with minute teeth. Fructification, blackish ovate seeds,
enveloped in pellucid cases, on both surfaces of the frond, aggregated
into waved transverse lines at unequal intervals, the intervals
occupied by similar seeds, solitary and scattered, or collected into little
spots. Substance thin and membranaceous, adhering to paper m drying.
Colour a bright pale reddish or yellowish olive-green, not changing on
exposure to the air.
Splendid specimens of this beautiful Alga have been communicated
to me by my friend Mrs Griffiths, from Sidmouth, in every desirable
state. The fructification, the substance, colour, and structure shew
that it is closely allied to the preceding species, though arranged by
Lamouroux, and since by Gaillon, among the Padina:. Specimens
from the coast of Normandy, kindly presented to me by M. Chauvin,
agree in every respect with our own. Two of them, however, represent
the plant less divided than is usual, and shew, that what may be
called the primary form of the frond, is not really that of the Padina:,
but is rather broadly wedge-shaped, without any tendency in the terminal
margin to continually extend itself at the lateral extremities in a
circular manner.
G e n u s X IX . CUTLERIA, Grev. Tab. X.
G e n . Ch a r . Frond piano-compressed, cartilagino-membra-
naceous, subflabelliform, irregularly cleft. Root a mass
of woolly filaments. Fructification, minute tufts of capsules,
scattered on both sides of the fro n d ; the capsules
pedicillate, containing several distinct granules.
O b s . It will be at once evident how much this genus differs from the
preceding, especially in the fructification. I cannot satisfy myself that
the capsules are situated at any period of their growth beneath the
epidermis, though such is the most natural conclusion. They are supported
upon long slender stalks, and contain about ten granules or