ere
exterminated during the cool period; but in somewhat depopulated areas,
into which there could be no migration, probably many closely allied
species will have been formed since this period. Hooker's paper in the
"Natural History Review" (364/2. Possibly an unsigned article, entitled
"New Colonial Floras" (a review of Grisebach's "Flora of the
British West Indian Islands" and Thwaites' "Enumeratio Plantarum
Zeylaniae").--"Nat. Hist. Review," January 1865, page 46. See Letter
184.) is well worth studying; but I cannot remember that he gives good
grounds for his conviction that certain orders of plants could not
withstand a rather cooler climate, even if it came on most gradually.
We have only just learnt under how cool a temperature several tropical
orchids can flourish. I clearly saw Hooker's difficulty about the
preservation of tropical forms during the cool period, and tried my best
to retain one spot after another as a hothouse for their preservation;
but it would not hold good, and it was a mere piece of truckling on my
part when I suggested that longitudinal belts of the world were cooled
one after the other. I shall very much like to see Agassiz's letter,
whenever you receive one. I have written a long letter; but a squabble
with or about Hooker always does me a world of good, and we have been
at it many a long year. I cannot understand whether he attacks me as a
wriggler or a hammerer, but I am very sure that a deal of wriggling has
to be done.

LETTER 365. TO J.D. HOOKER. Down, July 30th [1866].

Many thanks about the lupin. Your letter has interested me extremely,
and reminds me of old times. I suppose, by your writing, you would like
to hear my notions. I cannot admit the Atlantis connecting Madeira and
Canary Islands without the strongest evidence, and all on that side
(365/1. Sir J.D. Hooker lectured on "Insular Floras" at the Nottingham
meeting of the British Association on August 27th, 1866. His lecture is
given in the "Gardeners' Chronicle," 1867, page 6. No doubt he was at
this time preparing his remarks on continental extension, which take the
form of a judicial statement, giving the arguments and difficulties on
both sides. He sums up against continental extension, which, he says,
accounts for everything and explains nothing; "whilst the hypothesis
of trans-oceanic migration, though it leaves a multitude of facts
unexplained, offers a rational solution of many of the most puzzling
phenomena." In