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CONTRAST OF THE FLORAS. 373
CHAPTER IV.
CONTRAST of the floras in the different parts of the WORLD.—INSULAR AND CONTINENTAL FLORAS.—INCREASING RICHNESS OF VEGETATION IN THE DIRECTION FROM THE POLES TO THE EQUATOR.
Considered as a whole, the continents themselves, like the more restricted areas, present remarkable contrasts between their floras. Thus,
taking their disproportions as to extent into account, the New World appears to be much richer in species than the Old. This fact is explained
by the general disposition of the two Americas, and its chains of mountains almost all running in the direction from north to south. In consequence of the position of the Andes and the Cordilleras, the mountains of
Brazil, the Alleghanies, the Rocky Mountains, the Sierra Nevada, and the
Coast Range of California, it is found that under each latitude the most
various climates succeed each other on the opposite slopes, and, in consequence, different species are developed in each of these distinct climates.
In the Old World it is not thus, for most of the mountain chains — the
Pyrenees, the Alps, the Balkans, the Caucasus, Mount Taurus, the Himalayas, the Kafakorum, the Kuenlun, stretch in a direction from west to
east, and consequently the climates and floras are not modified in the
same direction, but by very gradual transitions. On the other hand, Af
rica, notwithstanding the situation ofthe greatest part of its mass under
the torrid zone, is relatively less rich than the other continents in species
of plants. This is explained by the general uniformity of the country, the
few high chains of mountains, and the very slight moisture of its winds.
But the southern extremity of Africa, the English colony of the Cape, is
exceedingly rich in plants.
Another contrast has been pointed out by several botanists—that of
the relative poverty of the insular, compared to the continental floras.
But this question is disputed, and the want of sufficient observations does
not allow us yet to decide it. Nevertheless, it is certain that the large
islands, such as Great Britain, Sicily, Cuba, and Ceylon, have types of vegetation entirely analogous to those of the neighboring continents; and
similarly, the Faroe Islands and Spitzbergen have as many species in proportion as the larger countries lying at an equal distance from the pole.
The archipelago of Cape Verd, the Canaries, Madeira, and the Azores
have, on the contrary, from three to five hundred species less than are
found on the same continental extent. Mauritius and Reunion have also
a relatively small number of indigenous plants; and it is quite natural to
think, with M. de Candolle, that the poverty of these islands proceeds in
great part from their long isolation in the open sea.
The principal fact in the distribution of plants over the surface of the
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000416 |
| Type | Books/Pamphlets |
| Transcript | CONTRAST OF THE FLORAS. 373 CHAPTER IV. CONTRAST of the floras in the different parts of the WORLD.—INSULAR AND CONTINENTAL FLORAS.—INCREASING RICHNESS OF VEGETATION IN THE DIRECTION FROM THE POLES TO THE EQUATOR. Considered as a whole, the continents themselves, like the more restricted areas, present remarkable contrasts between their floras. Thus, taking their disproportions as to extent into account, the New World appears to be much richer in species than the Old. This fact is explained by the general disposition of the two Americas, and its chains of mountains almost all running in the direction from north to south. In consequence of the position of the Andes and the Cordilleras, the mountains of Brazil, the Alleghanies, the Rocky Mountains, the Sierra Nevada, and the Coast Range of California, it is found that under each latitude the most various climates succeed each other on the opposite slopes, and, in consequence, different species are developed in each of these distinct climates. In the Old World it is not thus, for most of the mountain chains — the Pyrenees, the Alps, the Balkans, the Caucasus, Mount Taurus, the Himalayas, the Kafakorum, the Kuenlun, stretch in a direction from west to east, and consequently the climates and floras are not modified in the same direction, but by very gradual transitions. On the other hand, Af rica, notwithstanding the situation ofthe greatest part of its mass under the torrid zone, is relatively less rich than the other continents in species of plants. This is explained by the general uniformity of the country, the few high chains of mountains, and the very slight moisture of its winds. But the southern extremity of Africa, the English colony of the Cape, is exceedingly rich in plants. Another contrast has been pointed out by several botanists—that of the relative poverty of the insular, compared to the continental floras. But this question is disputed, and the want of sufficient observations does not allow us yet to decide it. Nevertheless, it is certain that the large islands, such as Great Britain, Sicily, Cuba, and Ceylon, have types of vegetation entirely analogous to those of the neighboring continents; and similarly, the Faroe Islands and Spitzbergen have as many species in proportion as the larger countries lying at an equal distance from the pole. The archipelago of Cape Verd, the Canaries, Madeira, and the Azores have, on the contrary, from three to five hundred species less than are found on the same continental extent. Mauritius and Reunion have also a relatively small number of indigenous plants; and it is quite natural to think, with M. de Candolle, that the poverty of these islands proceeds in great part from their long isolation in the open sea. The principal fact in the distribution of plants over the surface of the |
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