(Plantago major and lanceolata, Sonchus oleraceus,
and Artemisia vulgaris) are identical with European species.

The fact of a vegetation so closely allied to that of Europe occurring
on isolated mountain peaks, in an island south of the Equator, while all
the lowlands for thousands of miles around are occupied by a flora of
a totally different character, is very extraordinary; and has only
recently received an intelligible explanation. The Peak of Teneriffe,
which rises to a greater height and is much nearer to Europe, contains
no such Alpine flora; neither do the mountains of Bourbon and
Mauritius. The case of the volcanic peaks of Java is therefore somewhat
exceptional, but there are several analogous, if not exactly parallel
cases, that will enable us better to understand in what way the
phenomena may possibly have been brought about.

The higher peaks of the Alps, and even of the Pyrenees, contain a number
of plants absolutely identical with those of Lapland, but nowhere found
in the intervening plains. On the summit of the White Mountains, in
the United States, every plant is identical with species growing in
Labrador. In these cases all ordinary means of transport fail. Most of
the plants have heavy seeds, which could not possibly be carried such
immense distances by the wind; and the agency of birds in so effectually
stocking these Alpine heights is equally out of the question. The
difficulty was so great, that some naturalists were driven to believe
that these species were all separately created twice over on these
distant peaks. The determination of a recent glacial epoch, however,
soon offered a much more satisfactory solution, and one that is now
universally accepted by men of science. At this period, when the
mountains of Wales were full of glaciers, and the mountainous parts
of Central Europe, and much of America north of the great lakes, were
covered with snow and ice, and had a climate resembling that of Labrador
and Greenland at the present day, an Arctic flora covered all these
regions. As this epoch of cold passed away, and the snowy mantle of the
country, with the glaciers that descended from every mountain summit,
receded up their slopes and towards the north pole, the plants receded
also, always clinging as now to the margins of the perpetual snow line.
Thus it is that the same species are now found on the summits of the
mountains of temperate Europe and America, and in the barren north-polar
regi