Furi. 
+4 
t. 147,) a species from the Red Sea, resembling Lichen 
—y~" prunastri, and F. Valenti, (t. 78), brought also from 
the Red Sea, by the nobleman whose name it bears ; 
the “latter- rendered more remarkable by producing 
bright red aero tubercles, which form a striking 
contrast with the:glaucous frond. 
Some phenomena not uninteresting to the phy- 
siological chemist are slightly mentioned by Profes- 
sor Mertens in the: Allgemeine literatur Zeitung for 
1810, in his critique on Mr Turner’s£Zistory of Fuct. 
He states that F. ligulatus and 'F, viridis (.Turn. t. 97.) 
possess the property of suddenly altering the colour of 
other fuci along with which they h to be steeped 
in a vessel full of fresh water; the red colour of Conferva 
rubra, or Fucus ovalis, being changed to purple, and 
these plants rendered at the same time much more prone 
to decomposition, while the ligulatus and viridis remain 
unhurt.  F. viridis itself undergoes remarkable changes. 
While the plant is growing, it is of a deep rich orange ; 
but, says Mr Turner, “no botanist can have gathered 
it without being struck by the circumstance, that before 
he had conveyed it home, it had changed its original 
golden hue to a bright verdigris green.’? At the same 
time, it undergoes a change in its substance ; from 
being stiff and elastic, it becomes completely flaccid. 
Humboldt and Bonpland describe, * under the name of 
Fucus vitifolius,(as already mentioned,) a species of a fine 
grass green colour, brought-up, at J’Al za, from the 
great depth of 192 feet, at which depth it had vegetated. 
The light at that depth could only have been equal to half 
the light of an ordinary candle; yet, according to Hum- 
boldt’s experiments, common garden-cresses, exposed 
during vegetation to the light of two Argand’s lamps, 
acquire only a slight tint of green. . That distinguished 
philosopher therefore enciodes, date is only under the 
influence of the solar rays, however-weak,-that the car- 
buret of hydrogen is formed in the: of plants, the 
presence of which makes the eo appear of a 
lighter or darker green, according as the carbon prepon- 
derates in the mixture. 
The colour of all the soft and annual fuci depends 
on a very fugacious extractive. Those that are hor- 
ny in texture retain their colour with more force. | Se- 
veral of them become of a greenish hue when. boiled; 
and every one who has seen dulse fried, must have re- 
marked the change to green produced by the applica- 
tion of heat. The ultimate tendency to a green hue ob- 
servable in several species, may probably be ascribed to 
the more complete developement of the alkali contain- 
ed in the plant. 
To the botanist it may be useful to know, that when 
there is reason to suspect that the appearance of the 
plant.is changed by exposure to the air er rains, the 
original colour may often be detected by holding up 
the specimen against a strong light. For example, 
F. sinuosus, which is frequent on the stems of F. di- 
gitatus, and has fronds resembling in shape the leaves 
of Alnus incana, is, when fresh, of a rosy red colour ; 
in decaying on the shore, this changes first to violet, 
and then to tile red: but on holding the specimen 
against the light, the original rosy hue may be detected. 
Wahlenberg notices concerning F.)plumosus, that when 
repeatedly washed in. fresh water, it becomes green ; 
that, in dilute muriatic acid, it preserves its colour, 
and when removed front it becomes green, as if an al- 
kali had been poured on it. 
Another species, F. ericoides, (Turn. t..191:), pos- 
sesses the more extraordinary property of reflecting 
FUCL 
bright glaucous tints when seen under water in a grow- 
ing state. It is naturally of a sprriniecy jes colour, 
but under water appears as if in a state of vivid phos- 
phorescence. On withdrawing it from the sea, the 
brightness vanishes. The phenomenon has not been 
thoroughly examined. This fucus grows on the shores 
of Devonshire and Cornwall; but Mr Stackhouse, who 
spent his days in those districts, and had many oppor- 
tunities of observing the appearance, only says that the 
colour resides in, or is occasioned by a slimy mucus 
which covers the frond. When dried, the plant be- 
comes of a reddish brown colour. 
Concerning F. ligulatus, a species which occurs, 
though not plentifully, on our shores, and is ex 
ly figured by Lightfoot in his Flora, (t. 29,) Profes- 
sor Mertens mentions a curious fact: in. the sea it is 
of an olive green colour ; but as soon as it. is brought 
in contact with the air, it becomes of a deep orange, or 
rather the colour of decayed leaves. The only speci- 
mens we have seen, which were taken from the rub- 
bish of a fishing-boat at Newhaven in the Frith of 
Forth, were of a pale dull.green; but to this colour, 
Mertens observes, the orange tint soon declines. ; 
It-has been remarked of some of the smaller and 
more delicate fuci, that the same species seems to vary 
in appearance, size, and suena seaete: ing to 
the nature of the substance to whi 
larger sea-weed. But this observation is by no means 
of universal application. Variations are more generally 
occasioned. by the climate in which the plant grows ; 
the depth of avater ; the or sheltered nature of 
the situation ; or the proximity to the mouth of a river 
or body of fresh water. 
General Distribution of Fuci. 
- * . . General ; 
A few remarks on the general distribution of the fuci &hcr 
may here be made. Some may be considered as pro- 
perly ic, as F. pyriferus, (Turn. t.110), the gi- 
teus of Foster, or the badreuz of the Falkland Islan 
his sends out numerous fronds, and the upper and 
we fronds are frequently found anes it were 
er, at certain spots of the edges. is species 
omen so abundantly in the South American seas as to 
resemble islands, and it is one of the chief of the gigan- 
tic fuci alluded to by circumnayigators. Linnzus mere- 
ly says, that it is the longest and largest of the fuci. 
Solander measured some of the apices, and found 
them to be from ten to twelve feet; but he gives no 
guess as to the length of the entire plant, which is said 
to extend from 500 to 1000, or even 1500 feet. F. po- 
tatorum of Labillardiere, is another of the great pela~ 
gic fuci, of such ample dimensions, that particular parts 
of it furnish various household implements to the na- 
tives ef New Holland. 
Others, of a small size, which are never found but 
in the great ocean, may, it is thought, have originally 
been torn from the shores: this is the case with the nu- 
merous species which have long been confounded tos 
gether under the convenient name of Fucus natans, and 
which constitute the well known fields of floating sea- 
weeils met with in the great oceans. 
The fuci of the northern seas are in general different New Hol- 
in character and appearance from those of the tropics or 
of high southern latitudes. To take for example New 
Holland. . It is well known that the land plants of this 
singular country have a peculiar character, arising 
chiefly from many of the trees and shrubs being aphyl- 
* Plante quinoctiales, vol. ii. p. 8, t. 69. 
