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iiaceous, the cavity filled with a pellucid semifluid mass, and a fine network
of delicate filaments. Colour a pale pinkish-red. In drying, it
adheres closely to paper, and does not change colour.
The fructification of this, like that of the jireceding species, ajipears
to the naked eye like very minute dots, of a darker colour than the
frond. The globules of seeds are so firmly invested by a kind of tenacious
gelatinous limbus, that it is witli tbe utmost difficulty they can
be broken down upon the table of the microscope. The lower part
of the frond is said to be occasionally three-sided, but I have not observed
this conformation in any of tbe specimens I have examined in a
recent state, and suspect it may have been tbe result of partial exsiccation.
This appearance is represented iu one of tbe figures iu “ English
Botany,” while tbe other lias been evidently drawn, both plant and
analyses, from dried individuals.
G e n u s XLV. DUMONTIA, A«ww«-. Tuli. XViL
Ge n . C h a r . Frond cylindrical, simple or branched, membranaceous,
ttdnilar, gelatiiions witliin, of a red or pur-
plisb-red colour. Fructification, globules of seeds attached
to tlie inner 'surfiice of tbe membrane of tbe frond.
Obs. This genus was dedicated by the late Professor Lamouroux
to his friend M. Dumont, one of the authors of the Dictionnaire d’Histoire
Naturelle,.
The type of the species I consider to be the Ulva •purpurascens of
“ English Botany,” (not of Hudson), the fructification being more
clearly understood than in the other individuals of this group. The
globules and seeds are much larger than in the last genus ; the seeds
are not so tenaciously aggregated, and evidently attached to the inner
surface of the membrane of the frond, hut furnished with no orifice,
while the whole structure is more simple. Besides, the species mentioned
as the type, Halymenia ventricosa and saccata of Agardh, and
Dumontia fastigiata of Bory, belong this genus. Of Halymenia ramentacea,
Ag. I cannot speak with any certainty, having no specimen
in fructification. It is arranged by Agardh after his Halymenia f l i -
formis [Dumontia filiformis of this work), but from his account, I
suspect it will constitute a distinct genus. The specimen represented
by Mr Dawson Turner is unfortunately also without fi’uctification.
I. D u m o n t ia f i l i f o r m i s . Tab. XVII.
Frond filiform gelatinoso-membranaceous attenuated at each extremity
branched in a pinnato-fastigiate maimer the branches simple
elongated attenuated at the base.
Dumontia incrassata, L am o u r . E s s a i, p . 45.
Halymenia filiformis, A g . S p . A lg . v . 1 . p . 214. S y s t . A lg . p . 245.
Chondria purpurascens, G r e v . F L E d in . p . 290.
Gastridium filiforme, L y n g b . H y d r o p h . D a n . p . 68. t . 17- F i . D a n . t . 1664.
Solenia filiformis, S p r e n g . S p . P I . v . 4. p . 368.
Viva purpurascens, S m . E n g . B o t. t . 641.
Viva incrassata, F I . D a n . t . 653.
Ulva spohgiformis, F I . D a n . t . 763. f . 2.
Viva filiformis, F I . D a n . 1. 1480. f . 2.
V a b . /3. crispata ; f r o n d c om p r e s s e d w a v e d c u r le d a n d tw is te d , o f a b ro w n is h p u rp le
c o lo u r .
H a l y m e n i a purpurascens, vzx. crispata, G r e v . C r y p t . F I . t . 240.
H a b . On rocks and stones in the sea. Annual. Summer. Very
common. Var. g. in the Frith of Forth, opposite Seafield Baths,
Leith.
Root minute, scutate. Fronds solitary or somewhat tufted, cylindrical,
filiform, six to eighteen inches in length, varying in thickness
from a crow-quill to a goose-quill, or even more, flexuose, attenuated
both at the base and apex, more or less branched : the branches sometimes
numerous, given off almost in a distichous and pinnated manner,
sometimes few and fastigiate, but always flexuose, attenuated at each
extremity, and mostly undivided, varying greatly in length, some very
short, others as long as the entire plant. Fructif cation, globules or
clusters of large ovate seeds, attached to the inner surface of the coat
of the frond, and scattered plentifully throughout the whole plant, giving
it a mottled appearance to the naked eye. Substance membranaceous,
very gelatinous within. Colour varying from pale yellowish
dull red, to a deep brownish-red, livid or purple, changing to a dirty
green in decay. In drying, it adheres closely to paper, and does not
change colour materially.
The Ulva purpurascens of Hudson, being, on the authority of Mr
Dawson Turner, my Gastridium kalforme, it becomes requisite to
adopt the name under which the true plant is described in the Flora
Danica. It is a species of very frequent occurrence on our shores,
and sportive in its habit, but thereris no other British alga for whioh it
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