I have now got about a dozen seeds out of small birds' dung. Adios,
My dear Hooker, ever yours, C. DARWIN.
CHARLES DARWIN TO ASA GRAY. Down, January 1st [1857?].
My dear Dr Gray,
I have received the second part of your paper ('Statistics of the Flora of the Northern United States.' "Silliman's Journal", 1857.), and though I have nothing particular to say, I must send you my thanks and hearty admiration. The whole paper strikes me as quite exhausting the subject, and I quite fancy and flatter myself I now appreciate the character of your Flora. What a difference in regard to Europe your remark in relation to the genera makes! I have been eminently glad to see your conclusion in regard to the species of large genera widely ranging; it is in strict conformity with the results I have worked out in several ways. It is of great importance to my notions. By the way you have paid me a GREAT compliment ("From some investigations of his own, this sagacious naturalist inclines to think that [the species of] large genera range over a larger area than the species of small genera do."--Asa Gray, loc. cit.): to be SIMPLY mentioned even in such a paper I consider a very great honour. One of your conclusions makes me groan, viz., that the line of connection of the strictly alpine plants is through Greenland. I should EXTREMELY like to see your reasons published in detail, for it "riles" me (this is a proper expression, is it not?) dreadfully. Lyell told me, that Agassiz having a theory about when Saurians were first created, on hearing some careful observations opposed to this, said he did not believe it, "for Nature never lied." I am just in this predicament, and repeat to you that, "Nature never lies," ergo, theorisers are always right...
Overworked as you are, I dare say you will say that I am an odious plague; but here is another suggestion! I was led by one of my wild speculations to conclude (though it has nothing to do with geographical distribution, yet it has with your statistics) that trees would have a strong tendency to have flowers with dioecious, monoecious or polygamous structure. Seeing that this seemed so in Persoon, I took one little British Flora, and discriminating trees from bushes according to Loudon, I have found that the result was in species, genera and families, as I anticipated. So I sent my notions to Hooker to ask him to tabulate the New Zealand Flora for this end, and he thought my result sufficiently curious, to do so; and the accordance with Britain is very striking, and the more so, as he made three classes of trees, bushes, and herbaceous plants. (He says further he shall work the Tasmanian Flora on the same principle.) The bushes hold an intermediate position between the other two classes. It seems to me a curious relation in itself, and is very much so, if my theory and explanation are correct. (See 'Origin,' Edition i., page 100.)
With hearty thanks, your most troublesome friend, C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER. Down, April 12th [1857].
My dear Hooker,
Your letter has pleased me much, for I never can get it out of my head, that I take unfair advantage of your kindness, as I receive all and give nothing. What a splendid discussion you could write on the whole subject of variation! The cases discussed in your last note are valuable to me (though odious and damnable), as showing how profoundly ignorant we are on the causes of variation. I shall just allude to these cases, as a sort of sub-division of polymorphism a little more definite, I fancy, than the variation of, for instance, the Rubi, and equally or more perplexing.
I have just been putting my notes together on variations APPARENTLY due to the immediate and direct action of external causes; and I have been struck with one result. The most firm sticklers for independent creation admit, that the fur of the SAME species is thinner towards the south of the range of the same species than to the north--that the SAME shells are brighter- coloured to the south than north; that the same [shell] is paler-coloured in deep water--that insects are smaller and darker on mountains--more livid and testaceous near sea--that plants are smaller and more hairy and with brighter flowers on mountains: now in all such, and other cases, distinct species in the two zones follow the same rule, which seems to me to be most simply explained by species, being only strongly marked varieties, and therefore following the same laws as recognised and admitted varieties.