358 Scientific Reviews. 
polar zone, especially in the variety of species. But 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 Lamouroux, are 
rarely seen nearer to the Equator than 36°. Fucus serratus is entirely confined 
to Europe. If the imperfectly known Macrocystis comosa and Menziesii should 
prove to be true Fwei, the latter will bean exception to the rule, as it is said ‘to 
be found at 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 Fuc? diminish. In New Holland, remarkable 
alike for its vegetable and animal productions, a distinct group of Cystoseire pre- 
dominates, as singular in the water as the aphyllous Acacié are on the land. 
- Their stems are compressed, often appearing to be jointed; the branches spring 
from the flat side, and not from the angles, and are deflexed at their insertion ; 
besides which, their vesicles are solitary and pedicellate. This most extraordi- 
nary and local group, including some new species kindly communicated to me 
_by Mr. Fraser, the Colonial Botanist at Sidney, is already known to consist of 
twenty species. The genus Sargassum, the most extensive of the FucoipEs, 
comprising above seventy species, is nearly confined to the two Tropics, and ex- 
_amples rarely occur beyond the 42d degree in either hemisphere. ‘The Red Sea 
is full of Sargassa. It is principally to one or two species of Sargassum that 
.the popular name of gulf-weed, has been applied by mariners. The prodigious 
_accumulations of these plants were first encountered by the early Portuguese na- 
vigators : Columbus and Lerius compare them to extensive inundated meadows, 
and state, that they absolutely retarded the progress of the vessels, and threw the 
Sailors into consternation. Such accumulations occur on each side of the Equa- 
tor, in the Atlantic, Pacific and Indian Oceans ; but the sea, particularly deno- 
-mminated Mar de Sargasso by the Portuguese, stretches between the 16th and 
.22d parallels of north latitude, and the 25th and 40th meridians of west longi- 
;tude. Humboldt, in his Personal Narrative, describes the two banks of sea- 
weed that ocenr in the great basin of the Northern Atlantic Ocean ; but not hay- 
ing the passage at hand, I transcribe it in the words of Mr. Neill. ‘“‘ The most 
extensive is a little west of the meridian of Fayal, one of the Azores, between la- 
.titude 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 re- 
turning 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. It 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 be a question, but at what depth they vege- 
tate is still involved in obscurity. Neither is it clearly ascertained why the banks 
-of weed should always occur in the same places. ‘The supposition that they pro- 
ceed with the Gulf-Stream from the Gulf of Mexico—whence the original name 
of gulf-weed—is now exploded. Mr Neill justly observes, that the Gulf-Stream . 
would convey them rather to the banks of Newfoundland than to the latitudes in. 
which they usually occur; and it could not in any case accumulate them to the 
south of the Azores. Inthe genus Sargassum is observed a small group, as local 
and almost as peculiar as that we have shewn to exist in Cystoseira. This oc- 
curs in the seas of China and Japan, and consists of Sargassum fulvellum, mi- 
eroceratium, macrocarpum, sisymbrioides, Horneri, pallidum, and hemiphyllum, 
distinguished from the rest by terminal fructification, a slender habit, small nerve- 
less leaves, and often elongated vesicles. 
“ The LAMINARIE, among which are the giants of the marine flora, exhi- 
bit, in a broad view, a tolerably decided geographical distribution. The Lami- 
avi@ predominate from the 40th to the 65th degree of latitude ; while the AZacro- 
eystes 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 FLoripE&. This 
