It is a frightful assumption that the plains of Borneo were covered with a temperate cold vegetation that was driven up Kini Balu by the returning cold. Then there is the very distant distribution of a few Australian types northward to the Philippines, China, and Japan: that is a fearful and wonderful fact, though, as these plants are New Zealand too for the most part, the migration northward may have been east of Australia.
LETTER 374. TO J.D. HOOKER. December 24th [1866].
...One word more about the flora derived from supposed Pleistocene antarctic land requiring land intercommunication. This will depend much, as it seems to me, upon how far you finally settle whether Azores, Cape de Verdes, Tristan d'Acunha, Galapagos, Juan Fernandez, etc., etc., etc., have all had land intercommunication. If you do not think this necessary, might not New Zealand, etc., have been stocked during commencing Glacial period by occasional means from antarctic land? As for lowlands of Borneo being tenanted by a moderate number of temperate forms during the Glacial period, so far [is it] from appearing a "frightful assumption" that I am arrived at that pitch of bigotry that I look at it as proved!
LETTER 375. J.D. HOOKER TO CHARLES DARWIN. Kew, December 25th, 1866.
I was about to write to-day, when your jolly letter came this morning, to tell you that after carefully going over the N.Z. Flora, I find that there are only about thirty reputed indigenous Dicot. annuals, of which almost half, not being found by Banks and Solander, are probably non-indigenous. This is just 1/20th of the Dicots., or, excluding the doubtful, about 1/40th, whereas the British proportion of annuals is 1/4.6 amongst Dicots.!!! Of the naturalised New Zealand plants one-half are annual! I suppose there can be no doubt but that a deciduous-leaved vegetation affords more conditions for vegetable life than an evergreen one, and that it is hence that we find countries characterised by uniform climates to be poor in species, and those to be evergreens. I can now work this point out for New Zealand and Britain. Japan may be an exception: it is an extraordinary evergreen country, and has many species apparently, but it has so much novelty that it may not be so rich in species really as it hence looks, and I do believe it is very poor. It has very few annuals. Then, again, I think that the number of plants with irregular flowers, and especially such as require insect agency, diminishes much with evergreenity. Hence in all humid temperate regions we have, as a rule, few species, many evergreens, few annuals, few Leguminosae and orchids, few lepidoptera and other flying insects, many Coniferae, Amentaceae, Gramineae, Cyperaceae, and other wind-fertilised trees and plants, etc. Orchids and Leguminosae are scarce in islets, because the necessary fertilising insects have not migrated with the plants. Perhaps you have published this.
LETTER 376. TO J.D. HOOKER. Down, January 9th [1867].
I like the first part of your paper in the "Gard. Chronicle" (376/1. The lecture on Insular Floras ("Gard. Chron." January 1867).) to an extraordinary degree: you never, in my opinion, wrote anything better. You ask for all, even minute criticisms. In the first column you speak of no alpine plants and no replacement by zones, which will strike every one with astonishment who has read Humboldt and Webb on Zones on Teneriffe. Do you not mean boreal or arctic plants? (376/2. The passage which seems to be referred to does mention the absence of BOREAL plants.) In the third column you speak as if savages (376/3. "Such plants on oceanic islands are, like the savages which in some islands have been so long the sole witnesses of their existence, the last representatives of their several races.") had generally viewed the endemic plants of the Atlantic islands. Now, as you well know, the Canaries alone of all the archipelagoes were inhabited. In the third column have you really materials to speak of confirming the proportion of winged and wingless insects on islands?
Your comparison of plants of Madeira with islets of Great Britain is admirable.