New Caledonia these tribes become dess‘numerous ; and still
further southward the Austral temperate zone completely
changes the physiognomy of vegetation, and thé Isle? of Norfolk,
has, in common with New Holland, the Araucaniasj found
also in the harbour of Balade, and with New Zealand the
phormium tenax. It is, however, remarkable, • th a t this vast
island, composed of two lands separated by a channel, though
so near New Holland, and lying under the same latitudej-dif-
fers from it so completely, that they display no resemblance
in their vegetation. Yet New Zealand, so rich in genera peculiar
to its soil and little known, has some Indian plants, such
as Pepper, the Olea, and a renifortn fern, which is said to exist
in the Isle of Maurice.
The high lands of southern Polynesia between the tropics
partake-of the'alimentary plants of the Indian islands, which
have spread themselves in. different directions to the most
distant clusters, in a manner which it is difficult to explain,
since it is often contrary to the prevalent course of winds and
currents. Nearly all the high islands of Oceania bring forth
almost spontaneously bread-fruit-trees, the Aaro, or esculent
arum, sugar-canes and bananas. At Taiti is found th e Hibiscus
Rosa Sinensis, so abundant in the Moluccas ; the Pan-
danis Gardenia Florida, the Cyatheæ, the Cratæva, Figs
and Bamboos, there display their several tribes. 1 And it is qn
this island as M. d’Urville observes, that a multitude ôfiHpSia
begin to appear which inhabit this zone, spread hence and
even from the Marquesas to the Moluccas, some \§yen
reaching to the Isle of France. - Easter island, beyond the
tropic of Capricorn, presents but a small number of species,
and these are of Indian tribes ; such are hibiscus populneus,
some mimosas and a solanum, which the, younger Forster
found also a t Taiti.
$ u It is more easy to trace the way in which vegetation has
spread to the - low coral islands, and we have often followed
the difference stages of its progress. The flora here
consists but of a few species. The manner in which this in-?
teresting phenomenon has taken place, answers almost exactly
to the description, somewhat poetical, but true in its
main principles, of vegetable migrations, sketched in so delightful
a style,by M. Bernardin de St. Pierre, and M. Cha-
teaubriand.”
A review of the general bearing of the phenomena connected
with the ? vh|f#feiion of islands^ brings out results
strongly confirmatory ftp the dispersion of species from parti-
cular central points. -, Islands of considerable extent, and particularly
those of ancient formation, Jhough near to continents,
liaiVg*. in; several „instances peculiar systems qf i vegetation;
*hut where the flora of islands is, -not, peculiar, it is almost
everywhere precisely of that character which we., should anticipate
from the,local conditions and proximities of the mainlands
or. neighbouring - shores.
A comparison of the flora on thie differentfcq§stl > of inter-
tropical continents has developed, some ^relations, which we?
must not omit:,,to nqtice.
. Upwards of six hundred plants were, collected ;by Pijofesspr
Smith in the .neighbourhood ejjrithe river 'j Zaire, which have
been.compared by'Mr. Brown with the plants ?qf^otheTcoasts
within the tropics. - Of these six hundred
, Twenty-two are common to equinoctial Africa,. India, and,
America.
Thirteen.,are common to Africa and America; and unknown
in India.
Seventeen are common to Africa and India, and nqk.ip.uruf
in America.
Most,of these plants are strictly .equinoctial, and the^-,are,
such whose dispersion, cannot be ascribedto human, agenggf^
It was: observed by Mr. Brown, that most of them were,found
on the lower parts of-the river Zaire, where they form but^a,
small part of the entirelyegetation, and that m°st :of the dicotyledonous
plants in the list, are; such as produce seeds
capable of preserving their vitality a, long time in the currents
of the ocean, particularly those belonging tp the orders Malvaceae,
Convolvulaceae and Legumiposae, two, of which are
among the most numerous families on ;all equinoctial shores.
E