J' îi
il s
î i 'l if
situate oil any part of the ultimate pinnulæ, but never surrounded by
an involucre. Substance cartilaginous. Colour a fine dark purplish
red, sometimes pink in the young shoots, becoming brownish and
greenish-white in decay.
In var. /3, the fronds are tufted and aggregated, from two to six
inches long, bushy, much branched, the main stem and branches very
slender and nearly cylindrical, the pinnæ and pinnulæ crowded, short
and capillary ; the colour a black purplish-red ; the substance flaccid
and membranaceous. No fructification has been observed upon this
variety, except the granules destitute of an involucre above described.
Both varieties are somewhat darker when dried, g adheres closely
to paper, «. imperfectly.
So opposite are the two extremes of this plant, that they have quite
the aspect of distinct species ; but Mr Dawson Turner’s observation
is equally correct—“ That no Fucus whatever exhibits more regular
gradations between tbe most narrow and delicate, and the,broadest
and most cartilaginous individuals.” The most remarkable difference
between the two varieties recorded, consists in the' absence of the involúcrate
fructification, and the extreme flaccidity of variety g. The
latter character appears tp be in some way or other connected with
locality, for it is not observable in the narrowest and most delicate
specimens growing on Laminaria digitata. Variety g has the aspect
and texture of a delicate Conferva, and in its structure approaches
the jointed Algoe.
The smaller branches, pinnæ and pinnulæ, are distinctly divided by
pellucid dissepiments into nearly square joints. In variety « the same
structure is only evident in the pinnulæ, and at the extremity of the
branches. As a young pinna becomes elongated into a branch, smaller
cellules are added to the margin of the simple series of larger ones of
which it was at first composed ; thus a kind of symmetrical net-work is
formed, the whole consolidating, and becoming more and more obscure
as the part advances in age and increases in thickness.
The finest specimens I have ever seen of this species, were communicated
to me from the Orkney Islands, by the Reverend Mr Clouston.
One of these npw lying before me is intermediate between the
broadest and narrowest vaiieties, a foot in length, and completely covers
a large folio sheet of paper, many of the long branches lying over each
other.
The clusters of granules above described, which were formerly supposed
to occur only in variety g, I have found plentifully on the
broadest forms of variety «,
O r d e r X .— G A S T Î1 0C A R P EÆ .
Plants all mar ine, with a scutate root, o f a pink, red, or purplisk
red colour, most o f them not changing much on exposure to the
atmosphere, o f a carnose, gelatino-cartilaginous or gelatinoso-
membranaceous substance; the structure, consisting o f a cellular
external coat or membrane, and a pellucid gelatinous internal
mass, mostly traversed by colourless jointed filaments arising
from the outer membrane. Frond cylindrical, compressed, or
fia t, continuous, destitute o f midrib or veins. Fructification,
roundish clusters or globules o f red seeds imbedded in the internal
gelatinous substance o f the frond, and often unaccompanied
by an external pore.
G e n u s XLIII. IRIDÆA. Bory. Tab. XVII.
G e n . C h a r . Frond flat, expanded, carnose or gelatinoso-car-
tilaginous, more or less of a purplish red colour. Fructification,
globules of roundish seeds imbedded between
the two coats of tbe frond.
Obs. The present genus is proposed by Bory de St Vincent,- in the
Dictionnaire Classique d ’Histoire Naturelle, under a name ori'Ce suggested
by Stackhouse for some other plant. As it seems to be founded
in nature, and not to agree with the other Halymenioe of Agardh,
I willingly adopt it. I cannot think, however, of following M. Bory
de St Vincent, so far as to acquiesce in his ordinal arrangement,
and place it among the L a m i n a r i e æ , with which it has absolutely
no points in common except a flat frond, and the ocean for its habitation.
The Fucus edulis of Stackhouse is the type of this genus, and
representatives may be found in Fucus cordatus and reniformis of
Turner, Iridoea micans, laminaroides, and Augustinæ of Bory, and
perhaps in Fucus bracteatus of Gmelin. The Iridæoe have the frond
composed of two coats, constructed of a parallel series of vertical, moniliform,
coloured filaments, while the intermediate space is gelatinous