Dear Darwin

I had already read B. White’s paper, & corresponded with him about his conclusions. Unfortunately the Botany is all dead against him— There is no relationship whatever between the N. Atlantic Island Flora & that of S^t. Helena—¹

You have marked a passage to the effect that “one or two genera of plants common to S^t H. & S. Africa are strongly suggestive of a Palæarctic origin, & dispersion by the influence of a glacial epoch in for example Sium, which has an endemic-representative in S^t Helena & the very characteristic Cape genus Pelargonium, which has a straggler in Syria”.²

Now the Sium, which I first described, I have stated to be clearly allied to the S. Thunbergii of the Cape, which is no Palæarctic form; & how Pelargonium is to be classed as Palæarctic, because one species grows in Syria, whilst hundreds are confined to the Cape, which is its headquarters, passes my comprehension.³ I have come to the conclusion that the Flora of S^t. Helena is very S. African & not in the least North Atlantic; & as the plants must have got to S^t. Helena before the Insects, these must, if they came from the North, indicate that the Flora has survived the glacial epoch i.e. had come from the Cape before it.—

The difficulty of attributing to the Flora a Miocene age or origin is, the absence of any old types, such as Conifers & Cycads or examples of exceedingly limited (ie. dying out) Nat. Ords.⁴ If I remember aright most or all the plants belong to large & very cosmopolitan orders, well represented in S. Africa. Ascension does not help; it’s only shrubs are of South African affinity & S^t. Helena & these are if I remember aright its only flowering plants (except tropical weeds.) S^t. Helena has affinities with Tristan d’Acunha—⁵ If we could only make the insects antedate the plants I would understand the arguments

Is the Entomology of the S. African mountains known? especially of those Mts of the W. Coast.

What Frank will do is just what I want— De La Rue has promised me a note on the subject of Spottiswoode’s researches on Electric currents.⁶

Ever aff yrs | Jos. D. Hooker.

I am working hard at the Rocky Mt Flora, & find that it contains many old world genera & species not found in the equally lofty Sierra Nevada, which runs parallel to it for so many hundred miles.—& I am excessively interested about it.⁷ One would suppose that the migration along the American meridional ridges from the north southwards & back again was the simplest thing in the world— but it has not been so I am sure.

The Rocky Mt Flora will stand a very fair comparison with the Altai,⁸ which the Sierra Nevada will not