? !{
2. D e s m a r e s t ia a c u l e a t a . Tab. V. % s . 2. 3.
Stem short cylindrical soon terminating in a much branched linear-
filiform fiattish frond alternately and repeatedly pinnated, branches
solitary or in pairs, the pinnulæ set with erect subulate distichous
spines.
Desmarestia aculeata, L am o u r . E s s a i, p . 25.
Sporochnus aculeatus, Ag . S p . A lg . v . I . p . 151. S y s t. A lg . p. 259. G r e v . F I. E llin , p . 287.
S p r e n g . S p . P I . v . 4. p . 329.
Desmia aculeata, L y n g b . H y d r o p h . D a n . p . 34. t . 44. B. 1.
Fucus aculeatus, Lism. S p . P I . p . 1832. S ta c k h . N e r . B r i t . t. 8. T u r n . S y n . F u c . p . 262.
H is t. F u c . t. 187. S m . E n g . B o t. t . 2445.
H a b . in the sea. Perennial. Common on the British shores.
Root a hard disk. Frond without any midrib, one to three feet
long, very much branched in a distichous manner, all the branches and
branchlets much attenuated at their oiigin, sometimes two or even
three arising from the same point. The breadth hardly exceeds half a
line. When young the branches are beset with distichous pencils of
fine green conferva-like filaments, about a line apart, and three lines
long, which falling off are succeeded by little erect very acute spines,
scarcely a line in length. Fructification unknown.
Substance woody in the stem, cartilaginous, pliable, and very tough
in tbe branches. Colour olivaceous, but in the younger branches
green. Old plants do not adhere to paper in drying, and become a
little darker. Young plants still furnished with the pencils of filaments,
adhere, and do not change colour at all. If gathered in this
state it becomes soon flaccid, and, if allowed to remain in the vasculum
even for a short time, turns to a verdigris green, and destroys the Algæ
placed near it.
It is hardly possible to conceive a more beautiful object than this
plant waving its young and delicately feathered branches in the water.
When older and more robust, and furnished with spines instead of
tufts of filaments, it might easily be taken for a different species.
Though several naturalists have believed themselves to have detected
fructification, their accounts differ widely ; and it must still be regarded
as unknown. It would be unphilosophical to conjecture that, in a
perennial plant, the fructification could exist in such a part as the
pencils of filaments, which accompany the earliest efforts of vegetation,
and fall away long before the frond attains its natural size and strength.
In the true Sporochni, pencils very similar terminate an evident organ
of fructification, but they arc not deciduous till the plant has fully de39
veloped itself. The true Sporochni are, besides, if I mistake not,
either annual or biennial; but, at any rate, do not produce the little
tufts before the appearance of fructification.
G e n u s X. DICHLORIA, Grev. Tab. VI.
G e n . C h a r . Frond cylindrical, filiform, cartilaginous, pinnated
with opposite branches; becoming flaccid and of a
verdigris green colour on exposure to tbe air. Fructification
unknown.
O b s . This genus is the connecting link between Desmarestia and
Sporochnus, but differs in habit and structure from both. The interior
is composed of a mass of longitudinal jointed fibres, or, at least,
has a cellular tissue, which is so arranged as to separate into fibre-like
portions. There are no pencils of filaments, and, unlike all the species
of Desmarestia, the branches are not attenuated at their origin. It
possesses the remarkable property of decomposing most other Algae
placed in contact with it, after it has been removed from the water.
By Lamouroux, the single species composing this genus was placed
under Desmarestia ; by Agardh, it was made first a Chordaria, then
a Sporochus ; by Lyngbye a Gigartina-
The generic name is derived from the Greek numeral two, and the
word denoting a green colour; in allusion to its singular change of hue.
1. D ic h l o r ia v i r id i s . Tab. VI.
Sporochnus viridis, A g . S p . A lg . v . 1. p . 154. S y s t. A lg . p . 259. G r e v . F I . E d in . p . 28?.
S p r e n g . S p . P I . v . 4. p . 329.
Gigartina viridis, L y n g b . H y d r o p h . D a n . p . 44.
Desmarestia viridis, L am o u r . E s s a i, p . 25.
E r « » mW d is , F I . D a n . t . 886. T u r n . S y n . F u c . p . 397- H i s t . F u c . t . 97. S m . E n g . B o t.
t . 1669.
H a b . in the sea, gi-owing upon stones and the larger Algce. Annual.
Summer. Yarmouth beach, Mr Wigg. Scarborough, Sir T. Frank-
land- Beach at Brighton, Mr Borrer. Budleigh and Torquay,
Mrs Griffiths Bantry Bay, Miss Hutchins. At Lame, near Belfast,
Dr Drummond. Coast of Morayshire, Messrs Hooker and Borrer.
Frith of Forth, especially at Seafield rocks on'the Fife coast.
Root a small hard disk. Fronds one to several from the same base,