uch stronger put than you have. I am more reconciled to iceberg
transport than I was, the more especially as I will give you any length
of time to keep vitality in ice, and more than that, will let you
transport roots that way also.

(333/1. The above letter was pinned to the following note by Mr.
Darwin.)

In answer to this show from similarity of American, and European and
Alpine-Arctic plants, that they have travelled enormously without any
change.

As sub-arctic, temperate and tropical are all slowly marching toward the
equator, the tropical will be first checked and distressed, similarly
(333/2. Almost illegible.) the temperate will invade...; after the
temperate can [not] advance or do not wish to advance further the
arctics will be checked and will invade. The temperates will have been
far longer in Tropics than sub-arctics. The sub-arctics will first have
to cross temperate [zone] and then Tropics. They would penetrate among
strangers, just like the many naturalised plants brought by man, from
some unknown advantage. But more, for nearly all have chance of doing
so.

(333/3. The point of view is more clearly given in the following
letters.)

LETTER 334. TO J.D. HOOKER. Down, November 15th [1856].

I shall not consider all your notes on my MS. for some weeks, till
I have done with crossing; but I have not been able to stop myself
meditating on your powerful objection to the mundane cold period (334/1.
See Letter 49.), viz. that MANY-fold more of the warm-temperate species
ought to have crossed the Tropics than of the sub-arctic forms. I really
think that to those who deny the modification of species this would
absolutely disprove my theory. But according to the notions which I am
testing--viz. that species do become changed, and that time is a most
important element (which I think I shall be able to show very clearly
in this case)--in such change, I think, the result would be as follows.
Some of the warm-temperate forms would penetrate the Tropics long before
the sub-arctic, and some might get across the equator long before the
sub-arctic forms could do so (i.e. always supposing that the cold came
on slowly), and therefore these must have been exposed to new associates
and new conditions much longer than the sub-arctic. Hence I should
infer that we ought to have in the warm-temperate S. hemisphere more
representative or modified forms, and fewer identical species than in
comparing the colder regions of