To C. J. F. Bunbury   9 May [1856]¹

My dear Bunbury

I am extremely much obliged to you for the list,² which is capital & gives me as good an idea of the subject as one who is not a Botanist can have, & that I very deeply feel at the best is but a poor idea.— I shall be particularly glad, whenever you may have time & inclination, to hear anything which you may have to say on representative species (but I have not yet read Heer) & on my supposed cold mundane period.—³

When I most loosely spoke of all Europe, I was thinking of it in an E. & W. sense, which concerns me especially as showing the wide extension of the cold. I cannot prove this cold period geologically, I can only show that it is in some degree probable, & then if it explains a good many facts in distribution (45 algæ in New Zealand, common to the north & not found in Tropics), then I think it may be admitted as probable hypothesis. The several northern species in T. del Fuego, which during a cold period may have travelled down the Cordillera is one of the strongest cases. So many plants, some European, common to Himmalaya, Neilgherries, Ceylon, Java (I believe) & S. Australia. But My notions absolutely require some greater means of dispersal than A. Decandolle & Hooker are inclined to admit, but I cannot believe that we know 110 of means of dispersal. I stated on last Tuesday at Linnean Soc. (& I saw it made considerable impression on the cautious Bentham & on Lyell) that I had removed earth perfectly enclosed within roots of trees & in this earth (with every precaution taken) 3 seeds germinated; & I enumerated the oceanic islands on which I know trees (some with stones in roots) are cast up.⁴

But I shall weary you with my speculations & facts, so adios with many thanks | C. Darwin