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388 LIFE
preserved their latent life for thirty and forty centuries. Many geologists, indeed, believe that the rare plants suddenly springing up above
the remains of ancient fossiliferous strata originate really from seeds that
have been buried during a whole series of terrestrial revolutions.*
However it may be, such phenomena occur in too small a number of
plants for us to be able to explain in this way how so many vegetable
species having several habitats can flourish at a distance from the sea and
all highways of commerce, either in lakes and streams, or on the sides of
snowy mountains. We can only imagine two alternatives in the case of
these plants—either their germs have been developed spontaneously on
all the spots where the separate colonies are now found, and each mountain summit, each fluvial and lacustrine basin has become an independent
centre of vegetable generation; or else the snow-scattered colonies were
formerly connected with one another, and have been gradually separated,
or even displaced, in consequence of the changes of the surface or climates of the earth. The humble Alpine flowers, hiding in the snows and
in the crevices of rocks, would thus relate the great revolutions of the
globe.
In fact, during the earlier geological periods the mean temperature
underwent frequent changes, as the fossils in the strata of the earth
prove. In the same country the climate has been alternately hot, temperate, and cold; then it has become heated again, and consequently the
living organisms, plants and animals, have been incessantly displaced on
the surface of the earth.f Toward the end of the tertiary epoch, when
the regions which have now become the continents of Europe and North
America still enjoyed a high temperature, the vegetation must have had
a much more southerly character, on the whole, than in our days: in the
same way the scattered lands which surround the Arctic pole had doubtless a uniform flora, composed of plants analogous to those of our temperate zone. But the climate gradually changed, and the cold which was to
bring on the glacial period began to reign over the northern hemisphere.
There was a repulse ofthe species which had advanced too far toward the
north and missed the necessary warmth. They beat a retreat before the
snow and ice like an army in flight. The plants of the polar zone gained
little by little on the temperate zone, those of the temperate zone retreated toward the tropics, and, by the gradual encroachments of their colonies, even crossed the equator and established themselves on the now-
scorching plateaux and plains of the torrid zone. During the series of
centuries of an unknown length which elapsed during the glacial epoch
of our planet, a certain number of displaced species sought vainly to accommodate themselves in their new countries, and ended by succumbing;
while other plants, favored by the climatal conditions, grew without difficulty in the land of their exile, or even enjoyed greater prosperity there
than in their ancient abodes.
* Alph. de Candolle, Giographie Botanique, p. 1067.
t See The Earth, the section entitled The First Ages.
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000431 |
| Type | Books/Pamphlets |
| Transcript | 388 LIFE preserved their latent life for thirty and forty centuries. Many geologists, indeed, believe that the rare plants suddenly springing up above the remains of ancient fossiliferous strata originate really from seeds that have been buried during a whole series of terrestrial revolutions.* However it may be, such phenomena occur in too small a number of plants for us to be able to explain in this way how so many vegetable species having several habitats can flourish at a distance from the sea and all highways of commerce, either in lakes and streams, or on the sides of snowy mountains. We can only imagine two alternatives in the case of these plants—either their germs have been developed spontaneously on all the spots where the separate colonies are now found, and each mountain summit, each fluvial and lacustrine basin has become an independent centre of vegetable generation; or else the snow-scattered colonies were formerly connected with one another, and have been gradually separated, or even displaced, in consequence of the changes of the surface or climates of the earth. The humble Alpine flowers, hiding in the snows and in the crevices of rocks, would thus relate the great revolutions of the globe. In fact, during the earlier geological periods the mean temperature underwent frequent changes, as the fossils in the strata of the earth prove. In the same country the climate has been alternately hot, temperate, and cold; then it has become heated again, and consequently the living organisms, plants and animals, have been incessantly displaced on the surface of the earth.f Toward the end of the tertiary epoch, when the regions which have now become the continents of Europe and North America still enjoyed a high temperature, the vegetation must have had a much more southerly character, on the whole, than in our days: in the same way the scattered lands which surround the Arctic pole had doubtless a uniform flora, composed of plants analogous to those of our temperate zone. But the climate gradually changed, and the cold which was to bring on the glacial period began to reign over the northern hemisphere. There was a repulse ofthe species which had advanced too far toward the north and missed the necessary warmth. They beat a retreat before the snow and ice like an army in flight. The plants of the polar zone gained little by little on the temperate zone, those of the temperate zone retreated toward the tropics, and, by the gradual encroachments of their colonies, even crossed the equator and established themselves on the now- scorching plateaux and plains of the torrid zone. During the series of centuries of an unknown length which elapsed during the glacial epoch of our planet, a certain number of displaced species sought vainly to accommodate themselves in their new countries, and ended by succumbing; while other plants, favored by the climatal conditions, grew without difficulty in the land of their exile, or even enjoyed greater prosperity there than in their ancient abodes. * Alph. de Candolle, Giographie Botanique, p. 1067. t See The Earth, the section entitled The First Ages. |
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