erful effects of the Glacial period with respect to alpine
plants. (397/2. "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. Wallace's letter
to Darwin, dated January 1st, 1881, he evidently uses the expression
"passing through the air" in contradistinction to the migration of a
species by gradual extension of its