I have not yet attempted to count them up; but of course I am prepared
to believe that fully three-fourths of our species common to Europe will
[be] found to range northward to the Arctic regions. I merely meant that
I had in mind a number that do not; I think the number will not be
very small; and I thought you were under the impression that very few
absolutely did not so extend northwards. The most striking case I know
is that of Convallaria majalis, in the mountains [of] Virginia and North
Carolina, and not northward. I believe I mentioned this to you before.

LETTER 331. TO ASA GRAY. Down, October 12th [1856].

I received yesterday your most kind letter of the 23rd and your
"Statistics," and two days previously another copy. I thank you
cordially for them. Botanists write, of course, for botanists; but, as
far as the opinion of an "outsider" goes, I think your paper admirable.
I have read carefully a good many papers and works on geographical
distribution, and I know of only one essay (viz. Hooker's "New Zealand")
that makes any approach to the clearness with which your paper makes a
non-botanist appreciate the character of the flora of a country. It
is wonderfully condensed (what labour it must have required!). You ask
whether such details are worth giving: in my opinion, there is literally
not one word too much.

I thank you sincerely for the information about "social" and "varying
plants," and likewise for giving me some idea about the proportion (i.e.
1/4th) of European plants which you think do not range to the extreme
North. This proportion is very much greater than I had anticipated, from
what I picked up in conversation, etc.

To return to your "Statistics." I daresay you will give how many genera
(and orders) your 260 introduced plants belong to. I see they include
113 genera non-indigenous. As you have probably a list of the introduced
plants, would it be asking too great a favour to send me, per Hooker
or otherwise, just the total number of genera and orders to which the
introduced plants belong. I am much interested in this, and have found
De Candolle's remarks on this subject very instructive.

Nothing has surprised me more than the greater generic and specific
affinity with East Asia than with West America. Can you tell me (and I
will promise to inflict no other question) whether climate explains this
greater affinity? or is it one of the many utterly inexplicable problems
in botanical geograp