From J. D. Hooker   [16 November 1856]1

Dear Darwin

I write only to say that I entirely appreciate your answer to my objection on the score of the comparative rarity of Northern warm-temperate forms in the Southern Hemisphere.2 You certainly have wriggled out of it by getting them more time to change, but as you must admit that the distance traversed is not so great as the Arctics have to travel & the extremes of modifying cause not so great as the Arctics undergoe, the result should be considerably modified thereby.

Thus

The Sub Arctics have 1) to travel twice as far, 2) taking twice the time, 3) undergoing manyfold more disturbing influences.—

All this you have to meet by giving the North temp. forms simply more time—I think this will hardly hold water.

Ever Yrs | Jos D Hooker Kew Sunday

CD annotations

CD Note3: In answer to this show from similarity of American & European & Alp. Arctic plants, that they have travelled enormously without any change.4 As sub-arctic, temperate & Tropical are all slowly marching towards the equator, the Tropical will be first checked & [‘then’ del] distressed, then *some stray [interl] the temperate will invade, [illeg] to height or [even], *then come the struggle for life & death legion after legion in the long line of march from the far North [added pencil] after[‘wards’ del] the temperate can advance or do not wish to advance further, the arctics will be checked & will invade— The temperate will hence be far longer in Tropics than sub-arctic— The subarctic will be first here to cross temperate & then Tropics.— They wd penetrate amongst strangers just like the many naturalised plants brought by man, from some unknown advantage— But more, for nearly [interl] all have Chance of doing so—
3
This note follows the letter in DAR 100: 163.
4
In Natural selection, pp. 548–9, CD maintained that floras generally migrated in a body and did not experience different selective pressures until encountering a new of mixture of plants and animals. See letter to J. D. Hooker, 18 November [1856], and J. Browne 1983.

Please cite as “DCP-LETT-1622,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-1622