"Having been kindly permitted by Mr. Francis Darwin to read this letter, I
wish to explain that the above statement applies only to my rejection of
Darwin's view that the presence of arctic and north temperate plants in the
SOUTHERN HEMISPHERE was brought about by the lowering of the temperature of
the tropical regions during the Glacial period, so that even 'the lowlands
of these great continents were everywhere tenanted under the equator by a
considerable number of temperate forms ("Origin of Species," Edition VI.,
page 338). My own views are fully explained in Chapter XXIII. of my
"Island Life," published in 1880. I quite accept all that Darwin, Hooker,
and Asa Gray have written about the effect of the Glacial epoch in bringing
about the present distribution of alpine and arctic plants in the NORTHERN
HEMISPHERE."--Note by Mr. Wallace.) I do not know what you think, but it
appears to me that he exaggerates enormously the influence of debacles or
slips and new surface of soil being exposed for the reception of wind-blown
seeds. What kinds of seeds have the plants which are common to the distant
mountain-summits in Africa? Wallace lately wrote to me about the mountain
plants of Madagascar being the same with those on mountains in Africa, and
seemed to think it proved dispersal by the wind, without apparently having
inquired what sorts of seeds the plants bore. (397/3. The affinity with
the flora of the Eastern African islands was long ago pointed out by Sir
J.D. Hooker, "Linn. Soc. Journal," VI., 1861, page 3. Speaking of the
plants of Clarence Peak in Fernando Po, he says, "The next affinity is with
Mauritius, Bourbon, and Madagascar: of the whole 76 species, 16 inhabit
these places and 8 more are closely allied to plants from there. Three
temperate species are peculiar to Clarence Peak and the East African
islands..." The facts to which Mr. Wallace called Darwin's attention are
given by Mr. J.G. Baker in "Nature," December 9th, 1880, page 125. He
mentions the Madagascar Viola, which occurs elsewhere only at 7,000 feet in
the Cameroons, at 10,000 feet in Fernando Po and in the Abyssinian
mountains; and the same thing is true of the Madagascar Geranium. In Mr.