The generic name is derived from two Greek words, signifying a
net-work and a tube; the frond being tubular and reticulated.
1. DiCTYOStPHON PffiNICULACEUS. Tab. VIII.
Srytosiphon fceniculaceus, Ag . S p . A lg . v . I . p . KM. S y s t. A lg . p . 258. L y n g b . H y d r o p h .
D a n . p . 63. t. 14. ( u p p e r f ig u r e ) . S p r e n g . S p . P I . v . 4. p . 328.
Conferva fosniculacea, H u d s . F I . A n g . p . 594.
Fucus subtilis, T u m . H is t. F u c . t. 234.
H ab. In the sea, parasitic upon Chorda Filmn and some other Algce.
Annual. Spring and summer. Shores of Anglesea, Dillezdus. Cornwall,
Hudson. Bantry Bay, Miss Hutchins. Near Belfast, Dr
Drummond. Not uncommon on the western coast of Scotland, Turner.
Shores of the Isle of Bute. Frith of Forth.
Root an extremely minute disk. Fronds often numerous from the
same base, one to two feet long or more, the stem undivided, about
half a line or more iu diameter, but the whole frond otherwise capillary,
branched from the very bottom, tbe branches patent at their origin,
mostly alternate, sometimes partially secund, very irregular in
length, numerous or scattered, gradually attenuated to their extremity,
bearing a second series, half an inch or an inch in length, and as fine
as a hair, which, in their turn, produce a third series, still finer, and a
few lines only in length ; both the last series being set with an almost
invisible fringe of minute articulated filaments. Fructification ovate
scattered seeds slightly imbedded in the substance of the frond.
Substance membranaceous, or very slightly coriaceous, adhering to
paper in drying. Colour pale yellowish or olivaceous green, when
old, reddish, brownish, or blackish, not changing on exposure to the
air.
The appearance of this plant when growing, is very much that of
Dichloria viridis, especially if it be not injured from growing in an
exposed situation. When that is the case, many of the finer branches
disappear, and the soft feathery character is partly lost. Within the
tube, the surface is lined with pellucid oblong cellules. The fructification
requires close observation, and a high power of the microscope.
Lyngbye has represented one of the seeds pretty correctly, but the
larger of his uppermost figures is bad, and the seeds incorrect. Tbe
state observed by Lyngbye, represented in his lowest figure, I have
never been able to discover.
Genus X V llI. DICTYOTA, Lamour. Tab. X.
Ge n . Ch a u . Frond flat, higlily reticulated, membranaceous,
dicbotomous or irregularly cleft (palmato-flabelliform in
D. atomaria). Root a mass of woolly filaments. F ru ctification
composed of scattered or variously aggregated,
somewhat prominent, seeds, on both surfaces of the
frond.
Obs . This genus, originally jjroposed by Lamouroux, at first contained
that of Padina also, in the form of a section. But he afterwards
separated them, assigning to each the names they bear in this work.
Both of them ai e of earlier date than Zonaria, the name published by
Agardh, who reunited the two genera. They must of course be sustained
by the usual rights of courtesy and priority. Having carefully
examined most of the species in this and the following genera, I perfectly
accord with Lamouroux in his separation. The Dictyotce are of
a thinner and move membranaceous substance, producing their fructification
indifferently on both surfaces of the frond. The seeds are generally
scattered, hardly ever forming transverse lines, but when they do so,
they are not regular ones : They at length burst through the epidermis,
enveloped in their pellucid cases. The frond itself does not form
a regular segment of a circle when entire, and, when divided, the segments
have no tendency to assume the same form at their extremity.
Fven in one or two species, which are between palmate and flabelliform,
the margins of the segments exhibit no trace of laceration, but
are often denticulate, and evidently independent in every stage of
growth of the margin of the adjoining segment. There is also something
in the habit not easily expressed in words, which is very striking
, .
The name is derived from the Greek word for a net or net-work, m
allusion to the reticulated structure of the frond.
i: D ic t y o t a d ic h o t o m a . Tab. X.
Frond linear, regularly dichotomous.
Dictyota dichotoma, L am o u r . E s s a i, p . 58.
Zonaria dichotoma, Ag. S p . A.lg. v . 1. p . 133. S y s t. A lg . p . 266. G r e v . F I . E d in . p . 29?.
Haliseris dichotoma, S p r e n g . S p . P I . v . 4. p . 328.