Today | News | Books | Recipes Adventure | Science Fiction | Ghost stories | Poetry | Children | History Books, "it is inexplicable to me" how he
can compare the transport of seeds from the Andes to the Organ Mountains
with that from a continent to an island. Not to mention the much greater
distance, there are no currents of water from one to the other; and
what on earth should make a bird fly that distance without resting
many times? I do not at all suppose that nearly all tropical forms were
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 his lecture, Sir Joseph wrote that in ascending the
mountains in Madeira there is but little replacement of lowland species
by those of a higher northern latitude. "Plants become fewer and fewer
as we ascend, and their places are not taken by boreal ones, or by but
very few."): the depth is so great; there is nothing geologically in
the islands favouring the belief; there are no endemic mammals or
batrachians. Did not Bunbury show that some Orders of plants were
singularly deficient? But I rely chiefly on the large amount of specific
distinction in the insects and land-shells of P. Santo and Madeira:
surely Canary and Madeira could not have been connected, if Madeira and
P. Santo had long been distinct. If you admit Atlantis, I think you are
bound to admit or explain the difficulties.
With respect to cold temperate plants in Madeira, I, of course, know
not enough to form an opinion; but, admitting Atlantis, I can see their
rarity is a great difficulty; otherwise, seeing that the latitude
is only a little north of the Persian Gulf, and seeing the long
sea-transport for seeds, the rarity of northern plants does not seem to
me difficult. The immigration may have been from a southerly direction,
and it seems that some few African as well as coldish plants are common
to the mountains to the south.
Believing in occasional transport, I cannot feel so much surprise at
there being a good deal in common to Madeira and Canary, these being
the nearest points of land to each other. It is quite new and very
interesting to me what you say about the endemic plants being in so
large a proportion rare species. From the greater size of the workshop
(i.e., greater competition and greater number of individuals, etc.)
I should expect that continental forms, as they are occasionally
introduced, would always tend to beat the insular forms; and, as in
every area, there will always be many forms more or less rare tending
towards extinction, I should certainly have expected that in islands
a large proportion of the rarer forms would have been insular in their
origin. The longer the time any form has existed in an island into which
continental forms are occasionally introduced, by so much the chances
will be in favour of its being peculiar or abnormal in nature, and at
the same time scanty in numbers. The duration of its existence will
also have formerly given it the best chance, when it was not so rare, of
being widely distributed to adjoining archipelagoes. Here is a wriggle:
the older a form is, the better the chance will be of its having become
developed into a tree! An island from being surrounded by the sea will
prevent free immigration and competition, hence a greater number of
ancient forms will survive on an island than on the nearest continent
whence the island was stocked; and I have always looked at Clethra
(365/2. Clethra is an American shrubby genus of Ericaceae, found nowhere
nearer to Madeira than North America. Of this plant and of Persea, Sir
Charles Lyell ("Principles," 1872, Volume II., page 422) says: "Regarded
as relics of a Miocene flora, they are just such forms as we should
naturally expect to have come from the adjoining Miocene continent." See
also "Origin of Species," Edition VI., page 83, where a similar view is
quoted from Heer.) and the other extra-European forms as remnants of
the Tertiary flora which formerly inhabited Europe. This preservation of
ancient forms in islands appears to me like the preservation of ganoid
fishes in our present freshwaters. You speak of no northern plants on
mountains south of the Pyrenees: does my memory quite deceive me that
Boissier published a long list from the mountains in Southern Spain? I
have not seen Wollaston's, "Catalogue," (365/4. Probably the "Catalogue
of the Coleopterous Insects of the Canaries in the British Museum,"
1864.) but must buy it, if it gives the facts about rare plants which
you mention.
And now I have given more than enough of my notions, which I well know
will be in flat contradiction with all yours.
Wollaston, in his "Insecta Maderensia" (365/5. "Insecta Maderensia,"
London, 1854.), 4to, page 12, and in his "Va |