long. Several things are quite new to me in it--viz., for one, your belief
that there are more extra-tropical than intra-tropical species. I see that
my argument from the Arctic regions is false, and I should not have tried
to argue against you, had I not fancied that you thought that equability of
climate was the direct cause of the creation of a greater or lesser number
of species. I see you call our climate equable; I should have thought it
was the contrary. Anyhow, the term is vague, and in England will depend
upon whether a person compares it with the United States or Tierra del
Fuego. In my Journal (page 342) I see I state that in South Chiloe, at a
height of about 1,000 feet, the forests had a Fuegian aspect: I distinctly
recollect that at the sea-level in the middle of Chiloe the forest had
almost a tropical aspect. I should like much to hear, if you make out,
whether the N. or S. boundaries of a plant are the most restricted; I
should have expected that the S. would be, in the temperate regions, from
the number of antagonist species being greater. N.B. Humboldt, when in
London, told me of some river (14/3. The Obi (see "Flora Antarctica," page
211, note). Hooker writes: "Some of the most conspicuous trees attain
either of its banks, but do not cross them.") in N.E. Europe, on the
opposite banks of which the flora was, on the same soil and under same
climate, widely different!

I forget (14/4. The last paragraph is published in "Life and Letters,"
II., page 29.) my last letter, but it must have been a very silly one, as
it seems I gave my notion of the number of species being in great degree
governed by the degree to which the area had been often isolated and
divided. I must have been cracked to have written it, for I have no
evidence, without a person be willing to admit all my views, and then it
does follow.

(14/5. The remainder of the foregoing letter is published in the "Life and