gaiiized beings, and that this change is mainly owing to the
influence of temperature. L a m o u r o u x remarks, that if this
holds good, as we know it to do, to a wonderful extent in
phænogamous plants, it should also exert some corresponding
force upon marine vegetation. I t is unquestionable th a t the
Algoe are found on our own coasts, in the greatest abundance,
during the summer months, and in unusual luxuriance in hot
seasons. I t is probable also, observes the same authoi-, that
these plants may be acted on hy the temperature of the water
a t greater or less depths ; and th a t the species which grow at
the bottom of the ocean may have some resemblance to those
of the Polar Circle. On the shores of the British Islands it
is easy to perceive that some species, Gelidhm eorneum, Phyl-
lophora rubens, and Sphoerococcus coronopifoliiis, for example,
become more plentiful and more luxuriant as we travel from
north to south ; and, on the other hand, that Ptilota plumosa,
llkodomela lycopodioides, Rhodomenia sobolifera, and several
others, occur more frequently, and in a finer state, as we approach
the north. Odonthalia dentata, and Rhodomenia cris-
tata, arc confined to the northern parts of Great Britain,
while the Cystoseiroe, Fucus tuberculatus, Haliseris polypodi-
oides, Rhodomenia jubata, R . Teedii, Microcladia glandulosa,
Rhodomela pinastroides, Laurencia tenuissima, Iridoea renifor-
mis, and many others, are confined to the southern parts.
Others again, such as the Fuci in general, the L a m in a r ie æ ,
many Delesserioe, some Nitophylke, Laurentioe, Gastridia and
Chondri, possess too extended a range to he influenced by any
change of temperature between the northern boundary of
Scotland and the south-western point of England. The researches
and calculations of L a m o u r o u x have demonstrated
satisfactorily, th a t the great groups of Algoe do affect particular
temperatures or zones of latitude, though some genei'a
may he termed cosmopolite. Setting aside the great division
of articulated Algoe, of which we know but little, the
SiPHONEÆ, or at least the genus Codium, and the U l v a c
eæ , are scattered over every part of the world. Codium
tomentosum is found in the Atlantic, from the shores of England
and Scotland to the Cape of Good H o p e ; in the Pacific
from Nootka Sound to the southern coast of New Holland.
I t abounds in the Mediterranean, on the shores of France,
Spain, and Africa, and is common in the Adriatic. More
recently it has been also brought from the coasts of Chile
and Peru. This plant, however, is not a social one—to
make use of a term that H u m b o ld t has applied to some phee-
nogamous plants. I t grows even in the same locality, in a
solitary and scattered manner. The U l v a c e j ; , on the con^
trary, are strictly social, and pi-eserve this character in every
p a rt of the world. Tliey appear, however, to attain the
greatest perfection in the polar and temperate zones, although
I have very fine Porphyrce from the Cape of Good Hope.
That they are capable of sustaining very extreme cold, is
proved hy the fact, th a t fine specimens of Enteromorpha com-
pressa were picked up in high latitudes of the Arctic Ocean,
by some of the gentlemen who accompanied Captain Sir E d w
a r d P a r r y in his second Voyage of Discovery. The B ic -
TYOTE.E, of which we have eight representatives in Scotland,
and thirteen in England, increase both in quantity and number
of species, as we approach the Equator. The F u c o id E íE ,
in a general sense, increase as we leave the polar zone, especially
in the variety of species. Bu t the natural groups into
which they are separated, are strongly marked in their distribution.
The Fuci flourish between the latitudes 55° and 44°,
and, according to L a m o u r o u x , are rarely seen nearer to the
Equator than 36°. Fucus serratus is entirely confined to
Europe. I f the imperfectly known Macrocystis comosa and
Menziesii should prove to he true Fuci, the la tte r will he an
exception to the rule, as it is said to be found a t Trinidad, as
well as on the western coast of North America. The large
genus Cystoseira is found between the 50th and 25th degrees
of latitude, becoming more plentiful as the Fuci diminish.
In New Holland, remarkable alike for its vegetable and animal
productions, a distinct group of Cystoseirm predominates,
as singular in the water as the aphyllous Acacim are on the
land. Their stems arc «compressed, often appearing to be