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5. G a s t r id iu m -AKTicuLATUM.
Frond tubular contracted chain-like, branches fastigiate dichotomous
and whorled, capsules obtusely conical.
Chondria articuiata, Ag. S p . A lg . v. 1. p . 357. S y s t. A lg . p . 207- G r e v . F I . E d in . p . 291.
S p r e n g . S p . P I . v . 4. p . 342.
Lomentaria articulata, L y n g b . H y d r o p h . D a n . p . 101, t . 30. G a ill. in D ie t. Sc. N a t .
v . 53, p . 367.
Gigartina articulata, L am o u r . E s s a i, p . 49.
Fucus articulatus, L ig h t f . F I . S c o t. p . 959. S t a c k h . N e r . B r i t . p . 28. t. 8. T u r n . S y n .
F u c . p . 383. H i s t . F u c . t . 106. Sm . E n g . B o t. t . 1574.
H a b . In the sea, growing upon rocks and other Algce. Annual,
May to August. Not unfrequent on all the British shores. Coasts of
Cornwall, Devonshire, Dorsetshire, and Sussex, Hudson. Dover, Dillwyn.
Isle of Walney, Martyn. Coast of Northumberland, Winch.
Coast of Ireland, Miss Hutchins. Coasts of Jura, Oronsay, Canay,
Skye, &c. Lightfoot. Orkney, Rev. C. Clouston. Iona. Frith of
Forth.
Root a minute disk, accompanied with creeping fibres, which form
other disks from time to time, till the whole becomes an entangled
mass. Fronds numerous, bushy, much branched, one to six inches in
height, tubular, contracted at regular intervals in such a manner as to
present the appearance of a chain or necklace, the links or intervals
between the contractions varying, in different specimens, from two or
three lines to half an inch in length, and about a line in diameter,
those of the main branches being the longest. The primary divisions
of the frond are dichotomous or trichotomous : the smaller branches
whorled with repeated sets of spreading ramuli, all arising from the
contractions. Frucdif cation: 1. obtusely-conical minute capsules,
furnished with a pore, containing angular-ovate seeds, and situate on
the smaller' branches; 2. ternate granules imbedded in the younger
branches, on distinct plants.
Substance tender, between membranaceous and gelatinous, adhering
imperfectly to paper in drying. Colour a fine pinky red, sometimes
tinged with yellow or purple.
The principal variations to which this species is subject, consist only
in the thickness of the frond, the length of the contractions, and the
degree of ramification. In some specimens communicated from Devonshire
by Mrs Griffiths, the branches are elongated,, flagelliform, and
almost capillary, and, when growing, entangled and twisted like ten-
(Irils round the neighbouring plants. In Ireland, this Alga attains a
height of six inches, but in Great Britain rarely three or four. In
the Frith of Forth it seldom rises above two inches. The contractions
in the frond do not generally produce corresponding interruptions of
the internal structure. In some varieties, however, where the contractions
are strongly marked, the reverse seems to be the case.
M. Boiy de St Vincent has observed them produce internal septa,
which he even compares to those of the C o n f e r v o id e®.
G e n u s XXXIV. GRACILARIA, Grev. Tab. XIV.
G e n . C h a r . Frond cartilaginous, filiform, cylindrical or
compressed, of a dull red colour. Fructification; 1. capsules
containing a mass of minute roundish seeds; 2.
roundish or oblong simple granules imbedded in the
frond of distinct plants.
O bs. The plants which form this genus are distinguished from the
other filiform Sphcerococci of Agardh, 1. by a softer, more flexible, and
more transparent substance ; 2. by two modifications of the fructification—
capsules, and imbedded granules. The plants in which the
latter occur are mostly of a paler colour, and with dilated, or, as it
were, inflated, branches. The granules are never ternate. Mrs Griffiths
first pointed them out to me ; and I find, from an observation in
her Herbarium, that she has for several years considered Gracilaria
purpurascens and confervoides as plants with a double fructification.
The generic name is expressive of the slender habit of the species.
By Lamouroux this group was mingled with his Gigartince. In
Agardh’s System it forms a part of the genus Sphoerococcus ; but it
must be confessed, it has little in common with the tribe of Sphoerococcus
crispus and mamillosus ; or that of the pinnated species S. coronopifolius,
cartilagineus, &c. It comes, indeed, neai'est to the filiform
and cylindrical species, viz. S. plicata, acicularis, &c. ; but they
have a corneous substance, and one mode of fructification.