irds into quite new situations,
they have adapted themselves, by natural selection, to new
circumstances, changing the parts which required change--the leaves
and stalks; but keeping comparatively unchanged those which needed
no change--the flowers?

But I was not prepared, as I should have been had I studied my
Griesbach's West Indian Flora carefully enough beforehand, for the
next proof of the wide distribution of water-plants. For as I
scratched and stumbled among the tussocks, 'larding the lean earth
as I stalked along,' my kind guide put into my hand, with something
of an air of triumph, a little plant, which was--there was no
denying it--none other than the long-leaved Sundew, {260a} with its
clammy-haired paws full of dead flies, just as they would have been
in any bog in Devonshire or in Hampshire, in Wales or in Scotland.
But how came it here? And more, how has it spread, not only over
the whole of Northern Europe, Canada, and the United States, but
even as far south as Brazil? Its being common to North America and
Europe is not surprising. It may belong to that comparatively
ancient Flora which existed when there was land way between the two
continents by way of Greenland, and the bison ranged from Russia to
the Rocky Mountains. But its presence within the Tropics is more
probably explained by supposing that it, like the Bladder-worts, has
been carried on the feet or in the crop of birds.

The Savanna itself, like those of Caroni and Piarco, offers, I
suspect, a fresh proof that a branch of the Orinoco once ran along
the foot of the northern mountains of Trinidad.

'It is impossible,' says Humboldt, {260b} 'to cross the burning
plains' (of the Orinocquan Savannas) 'without inquiring whether they
have always been in the same state; or whether they have been
stripped of their vegetation by some revolution of nature. The
stratum of mould now found on them is very thin. . . . The plains
were, doubtless, less bare in the fifteenth century than they are
now; yet the first Conquistadores, who came from Coro, described
them then as Savannas, where nothing could be perceived save the sky
and the turf; which were generally destitute of trees, and difficult
to traverse on account of the reverberation of heat from the soil.
Why does not the great forest of the Oroonoco extend to the north,
or the left bank of that river? Why does it not fill that vast
space that reaches as