To C. J. F. Bunbury 9 May 1
Down Bromley Kent
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
On geographical dispersal of plants. Would be interested in CJFB’s views on representative species and on his hypothesis of a mundane cold period, which CD cannot prove geologically, but thinks, if it explains many facts of geographical distribution, may be admitted as probable. Hooker and Alphonse de Candolle do not agree with him.