jointed ; the hiiinches spring frqm tlie flat side, and not
from the angles, and are deflexed at their insertion ; besides
which, their vesicles are solitary and pedicellate. This
most extraordinary and local group, including some new
species kindly communicated to me hy Mr F r a s e k , the Colonial
Botanist at Sidney, is already known to consist of
twenty species. The genus Sargassmn, the most extensive of
the F u c o id e æ , comprising above seventy species, is nearly
confined to the two Tropics, and examples rarely occur beyond
the 42d degree in either hemisphere. Tlie Red Sea is
full of Sargassa. I t is principally to one or two species of
Nar<7iwSMmthat the popular name oigulf-weed, has been applied
hy mariners. The prodigious accumulations of these plants
were first encountered hy the early Portuguese navigators :
C01.UMBUS and L e r iu s compare tliem to extensive inundated
meadows, and state, th a t they absolutely retarded the progress
of the vessels, and threw the sailors into consternation. Such
accumulations occur 011 each side of the Equator, in the A tlantic,
Pacific and Indian Oceans ; but the sea, particularly
denominated Mar do Sargasso hy tlie Portuguese, stretches
between the 18tli and 22d parallels of north latitude, and the
25tli and 40th meridians of west longitude. H u m b o l d t , in
his Personal Narrative, describes the two hanks of sea-weed
that occur in the great basin of the Northern Atlantic Ocean ;
but not having the passage a t hand, I transcribe it in the
words of Mr N e i l l . “ The most extensive is a little west of
the meridian of Fayal, one of the Azores, between latitude
25° and 36°. Violent north winds sometimes prevail in this
space, and drive the sea-weed to the low latitudes, as far as
24° or even 20°. Vessels returning to Europe, either from
Monte Video or the Cape of Good Hope, cross the bank
nearly at an equal distance from the Antilles and Canaries.
The other occupies a much smaller space between 22° and
26°, eighty leagues west of the meridian of the Bahama
Islands. I t is generally traversed by vessels on the passage
from the Caicos to the Bermudas.” That these plants are
produced within the tropics, there can hardly he a question,
hut at wliat deptli they vegetate is still involved in obscurity.
Neither is it clearly ascertained why the banks of
weed should always occur in the same places. The supposition
tliat they proceed witli the Gulf-Strcam from the Gulf
of Mexico—whence the original name of gulf-weed—is now
exploded. Mr N e i l l justly observes, that the Gulf-Stream
would convey them rather to the' hanks of Newfoundland
than to the latitudes in which they usually occur; and it could
not iu any case accumulate them to the south of the Azores.
Ill the genus Sargassum is observed a small group, as local
and almo.st as peculiar as that we have shewn to exist iu Cystoseira.
This occurs in the seas of China and Japan, and consists
of Sargassum fulvellum, microceratium, macrocarpum,
sisymhrioides, Horneri, pallidum, and hemiphyllum, distinguished
from the rest by terminal fructification, a slender
habit, small nerveless leaves, and often elongated vesicles.
Tlie LAMiNARiEiE, among whicli are the giants of the marine
flora, exhibit, in a broad view, a tolerably decided geographical
distribution. The Lamntarice predominate i'rom
the 40th to tlie 65th degree of la titu d e ; while the Mucrocystes
seem, as far as we know, to exist from the Equator to about
45° of south latitude.
The only order of any extent remaining to be noticed is
F lo r id e / E . This order, generally speaking, belongs, according
to L a m o u r o u x , to the Temperate Zones; and in tliis
coiicludon I think he is correct. But, as might he anticipated,
in an order which contains so large a inimhor of genera
and species, there are many exceptions. The genus Amansia
IS exclusively tropical. Hypnma and Acanthophora belong
also, rather to the tropical than the neighbouring zones. It
IS worthy of notice, that, comparatively speaking, the soutlierii
temperate zone contains much fewer FuoRiDEiE than the
northern : a fact that L a m o u r o u x thinks may he accounted
for hy the inferior extent of the temperate zone in that lie-
misphere.
From the number of species known to L a m o u r o u x , he
calculated that the F l o r id e . ® predominate greatly over tlie