en those points{363}. I believe, however, this anomalous
case admits, as we shall presently see, of some explanation. We might
have expected that the flora of a mountain summit would have presented
the same relation to the flora of the surrounding lowland country, which
any isolated part of a continent does to the whole, or an island does to
the mainland, from which it is separated by a rather wide space of sea.
This in fact is the case with the plants clothing the summits of _some_
mountains, which mountains it may be observed are particularly isolated;
for instance, all the species are peculiar, but they belong to the forms
characteristic of the surrounding continent, on the mountains of
Caraccas, of Van Dieman's Land and of the Cape of Good Hope{364}. On
some other mountains, for instance <in> Tierra del Fuego and in Brazil,
some of the plants though distinct species are S. American forms; whilst
others are allied to or are identical with the Alpine species of Europe.
In islands of which the lowland flora is distinct <from> but allied to
that of the nearest continent, the Alpine plants are sometimes (or
perhaps mostly) eminently peculiar and distinct{365}; this is the case
on Teneriffe, and in a lesser degree even on some of the Mediterranean
islands.

{362} See _Origin_, Ed. i. p. 365, vi. p. 515. The present
discussion was written before the publication of Forbes' celebrated
paper on the same subject; see _Life and Letters_, vol. I. p. 88.

{363} The apparent breakdown of the doctrine of barriers is
slightly touched on in the _Origin_, Ed. i. p. 365, vi. p. 515.

{364} In the _Origin_, Ed. i. p. 375, vi. p. 526, the author points
out that on the mountains at the Cape of Good Hope "some few
representative European forms are found, which have not been
discovered in the inter-tropical parts of Africa."

{365} See Hooker's _Lecture on Insular Floras_ in the _Gardeners'
Chronicle_, Jan. 1867.

If all Alpine floras had been characterised like that of the mountain of
Caraccas, or of Van Dieman's Land, &c., whatever explanation is possible
of the general laws of geographical distribution would have applied to
them. But the apparently anomalous case just given, namely of the
mountains of Europe, of some mountains in the United States (Dr Boott)
and of the summits of the Himalaya (Royle), having many identical
species in common conjointly with the Arctic regions, and