e., by specific centers of
their own, and partly by an assemblage more or less limited in the several
ranges of identical species, these latter in several cases so numerous that
ordinary modes of transportation now in action can no more account for their
presence than they can for the presence of a Norwegian flora on the British
mountains. Now I am prepared to maintain that the same means which
introduced a sub-Arctic (now mmountain) flora into Britain, acting at the
same epoch, originated the identity, as far as it goes, of the Alpine floras
of middle Europe and Central Asia; for, now that we know the vast area swept
by the glacial sea, including almost the whole of Central and Northern
Europe, and belted by land, since greatly uplifted, which then presented to
the water's edge those climatal lconditions for which a sub-Arctic flora --
destined to become Alpine -- was specially organized, the difficulty of
deriving such a flora from its paarent north, and of diffusing it over the
snowy hills bounding this glacial ocean, vanishes, and the presence of
identical species at such distant pooints remain no longer a mystery.
Moreover, when we consider that conditions during the epoch referred to, the
undoubted evidences of Continental observers, on the boounds of Asia by Sir
Roderick Murchison, in America by Mr.
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