O r d e r V I— D IC T Y O T E Æ .
Plants all marine, o f an olive-green colour, not changing on exposure
to the air, o f a membranaceous flexible siéstance (rarely
cart dag hums) and retiezdated strzicture. Root either naked
and scutate, or composed o f a znass o f woolly filaznezits. Frond
cylindrical or f la t ; when fla t, nerveless (except in Haliseris ) ,
thin, entire or divided, often flahelliforzn. Fructification,
roztndish, ovate, pear-shaped or club-shaped seeds, enveloped
in a pellzzcid case, covering the szirface, or scattered, or form-
hig znhiute spots or trazisverse lines. The seeds in most cases
are produced bezieath the epidermis, through which they burst,
and become proznizient.
G e n u s X III. CHORDA, Stackh. Laznour. Tab. VII.
G e n . C h a r . Frond simple, filiform, cylindrical, with an interrupted
cavity. Root naked, scutate. Fructification
external continuous masses of pear-shaped seeds fixed by
their base.
The genus Chorda proposed by Stackhouse, adopted by Lamouroux,
and continued by Lyngbye and by Hooker, possesses a priority of many
years over the name Scytosiphon, of my friend Professor Agardh. As
the original name is, besides, employed by the majority of authors,
no inconvenience can arise from the justness of its claim being recognised.
The Fucus Filum of Linnæus forms the type of the genus
which contains only two species. What Agardh calls Scytosiphon
foeniculaccus [Fucus subtilis, Turn.), possesses a very different structure
and a totally different fructification. This fructification, which is
represented pretty correctly by Lyngbye, agrees with that of some
Dictyotce, as does also the structure and substance.
By Lamouroux and Agardh, Chorda is placed among the Fucoi-
DEÆ : by Gaillon among the jointed Algæ, on account of the transverse
interruptions of the internal cavity. To me it appears to be very
nearly related to Aspcrococcus and other D ictyoteæ, especially in the
fructification. The generic name is derived from the Latin word signifying
a cord or string.
1. C h o r d a R il u m . Tab. VII.
Frond cartilaginous much elongated, the transverse septa not accompanied
by external constriction.
Chorda Filum, L am o u r . E s s a i, p . 26. L y n g b . H y d r o p h . D a n . p . 79. t . 18. H o o k , in F I.
L o n d . N ew S e r ie s , t . 204.
Scytosiphon Filum, A g . S p . A lg . v . I . p . 161. S y s t . A lg . p . 25?. G r e v . F I . E d in . p . 288.
S p r e n g . S p . P I . v . 4. p . 328.
Fucus Filum, L in n . S p . P I . p . 1G31. S ta c k h . N e r . B r i t . 1 . 10. T u r n . S y n . p . 339. H is t.
F u c . t . 86. Sm . E n g . B o t. t . 2487-
V a r . |S Thrix. F r o n d v e r y s le n d e r , a lm o s t c a p illa ry , tw o to f o u r in c h e s in le n g th .
Chorda Filum v . trichodes, L y n g b . p . 7 3 . 1 . 18.
Scytosiphon Filum v . Thrix, Ag . S p . A lg . v . 1. p . 162.
Fucus Thrix, S t a c k h . N e r . B r i t . p . 25. t . 12.
H a b . In the sea, attached to rocks and stones. Annual. Summer
and autumn. Very common on the British shores.
Root a very small conical disk. Fronds generally several from the
same base, quite simple, one to twenty feet in length, cylindrical, one-
eighth of an inch to half an inch in diameter in the middle, much attenuated
at each extremity, hollow, the cavity interrupted at short
intervals by transverse divisions: the whole frond spirally twisted
from the base to the apex. Fructification, pyriform capsules, covering
the surface in a nearly continuous mass, and fixed by their base.
In the growing state the whole plant is fringed with delicate filaments
one to two lines in length, which give it a slippery feel. In
some states these filaments are more numerous, obvious, and of a
brownish green colour. The plant then forms the Chorda tomentosa
of Lyngbye.
Substance cartilaginous, lubricous, elastic and tough, adhering to
paper in drying. Colour an olivaceous, somewhat transparent green,
becoming somewhat darker when dry.
The fructification of this Alga was for a long time a desideratum.
It was first represented in “ English Botany,” from specimens collected
by Mr Borrer ; afterwards, not very perfectly, in the “ Tentamen
Hydrophytologiæ Danicæ.” Agardh describes it correctly. A second
kind of fructification, composed of sessile, ovate capsules, scattered
among clavate, articulated filaments, is recorded in the “ Flora Lon-
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