length and breadth, liaving also a general tendency in most instances to
subdivide in a laciniated manner. In this respect, Halymenia differs also
from the following genera of the order, which are more simple in their
ramification. The substance is thinner, more tender and gelatinous
than in Iridoea, the structure more simple, especially in the external
membrane, and there is a less complicated tissue of fine filaments occupying
the interior. I have not been able to perceive the least trace
of any orifice for the escape of the seeds.
To this genus belong Fucus jloresius of Clemente, Halymenia
variegata and Durvillæi of Bory, Fucus usnea of Brown, Halymenia
furcellata and trigona of Agardh, and perhaps also Halymenia platyna
of the same author.
The literal interpretation of the generic name is Sea-membrane.
1. H a ly m e n ia l i g u l a t a . Tab. XVII.
Frond hetween compressed and plane irregularly dichotomous the
axils rounded the segments linear attenuated towards the apex, and
often throwing out simple frondlets from the margin.
Halymenia ligulata, A g . S p . A lg . v . 1. p . 210. S y s t. A lg . p . 244. S p r e n g , S p . P I . v . 4.
p . 333.
Halymenia elongata, Ag. S p . A lg . v . 1. p . 209. S y s t. A lg . p . 243.
Viva ligulata, W o o dw . in L in n . T r a n s , v . 3. p . 54. Sm . E n g . B o t . t . 420. a b a d fig u re .
Viva rubra, H u d s . F I . A n g l. p . 571. S m . E n g . B o t. 1. 1627.
Dumontia ineequalis, L am o u r . in l e t t e r , a c c o rd in g t o A g a rd h .
Mesogloia Htidsoni, Ag. S y s t. A lg . p . 50.
Mesogloia multifida, S p r e n g . S p . P I . v . 4. p . 370, a s f a r a s r e g a r d s t h e s y n o n ym o f Viva
rubra.
H a b . On rocks and stones in the sea. Annual. Summer. On
Yarmouth Beach, Mr Wigg- On rocks at Cromer, Mr Woodward.
At Sheringham, Turner. Beach at Gorton and Gunton, Suffolk,
Mrs Fowler. At Christ Church, Hudson. Coast of Anglesea, Rev.
H. Davies. Brighton, Dillwyn. Weymouth, Rev. M. J. Berkeley.
Sidmouth, Mrs Griffiths. Ilfracombe, Miss Cutler.
Root a small disk. Fronds tufted, two to near twelve inches in
length, attenuated at the base, between compressed and flat, dichoto-
mously divided, the segments very few or very numerous, from two
lines to three-fourths of an inch in width, either equal aud rounded,
or attenuated at the extremity, the axills of the dichotomies obtuse,
the margin entire, or sometimes fringed with little simple or forked
frondlets, an inch in length or more, and attenuated at their base.
Fructification very minute globules of seeds scattered over the whole
frond, and imbedded in the gelatinous central substance. Substance
gelatinous and membranaceous, somewhat transparent. Colour a pinky
red, the globules of seeds darker. In drying, it adheres closely to paper,
and does not change colour.
By means of specimens collected by Miss Cutler at Ilfracombe, I
have been induced to refer Halymenia elongata, Ag. without any
hesitation, to this species. These specimens are ten inches in length,
nearly an inch wide, only twice dichotomous, the terminating segments
either rounded or emarginate, the margins quite entire. From this
state of the plant, I possess specimens which lead insensibly to Uha
rubra of Hudson,—the opposite extreme, which unquestionably belongs
to this place, and is probably a dwarfish state, owing to some
peculiarity of situation. A specimen kindly communicated by the
Rev. Mr Berkeley, from Weymouth, under the name of Ulva rubra,
is little more than an inch in length, but is nevertheless in fructification.
Sprengel has adopted an error of Lyngbye, and united the Ulva
rubra to Mesogloia multifida of Agardh.
It is worthy of remark, that the smaller specimens are the most irregular
in the division of the frond. Some present not unfrequently,
laciniate extremities, others have them palmated.
2. H a l y m e n ia f u r c e l l a t a .
Frond gelatinoso-membranaceous uniformly dichotomous the segments
filiform cylindrical, the extremities sublanceolate.
Halymenia f urcellata, A g . S p . A lg . v . I . p . 212. S y s t. A lg . p . 244. S p r e n g . S p . P I . v . 4.
p . 333.
Viva furcellata, T u r n , in S c h r a d . J o u r n . v . 2. p . 301. Sm . E n g . B o t. t. 1881.
Dumontia triquetra, L am o u r . E s s a i, p . 45.
H a b . On rocks and stones in the sea. Annual. Summer. At
Sheringham, Norfolk, Turner. Shore at Yarmouth, Mr Wigg. Coast
of Suffolk, Mrs Fowler. Southampton, Miss Biddulph. Sidmouth,
Mrs Griffiths. Torquay.
Root a minute disk. Frond one to four inches long, filiform, cylindrical,
divided from the base many times in a regularly dichotomous
manner, segments about a line in thickness, somewhat erect, crowded,
distended with moisture so as to appear inflated, the ultimate ones
elliptic-lanceolate. Fructification minute punctiform globules of seeds
imbedded beneath the membranaceous cellular coat of the frond, which
is not perforated by any orifice. Substance gelatinous and membra-
L 2
■I