To J. D. Hooker 1 July 1
Down Bromley Kent
My dear Hooker
I write to say how truly I think you the best of men for proposing to pay us a visit this summer, I shall most truly & heartily enjoy it. In a few weeks time we shall know our plans better, as Etty & our Boys holidays make everything doubtful I am alone at present Emma visiting some relations with a tail of six children!2 I am very sorry to hear about G. Henslow: an attack of religion is a most serious thing: the whole affair must be a great disappointment to you.—3
Thanks for your interesting note about embryonic leaves: after I had sent it, I began to think about cotyledons, & marvelled that I could not remember having ever read any discussion on their resemblances & dissimilarities in allied plants. How curious that the subject shd never have been taken up! I do not even know whether functions of the cotyledons are same as leaves, or whether they serve, also, as receptacle of nutriment: I have noticed in my weed-garden that their destruction seems always to kill the plant.— I was speculating in my ignorance that the form of cotyledon was probably related to the shape of seed & its embryo & radicle; & if this were so, as seeds are adapted to various contingencies, we might expect the cotyledons to differ; but probably this is not the case, as it wd have occurred to you. I am not learned enough in animal embryology to compare cotyledons with amnios &c &c.—
If cotyledons have a relation to the external conditions of existence distinct or partially different from what the leaves of the mature plant have to the conditions, I think the differences of the cotyledons in the same Family, would be explicable in the same way as in some Diptera & some Neuroptera, there is a wonderful amount of difference in the larvæ:— no doubt these larvæ have much in common, & so I presume the cotyledons have much in common.
I have had another letter from Asa Gray: most kindly he has worked out trees of U. States & finds out of 132, 95 have sexes more or less separate (= .72); so that the Rule seems here to hold good whether or no my explanation is correct.4
Farewell | My dear Hooker | Ever yours | C. Darwin
George Henslow’s curtness to JDH: "an attack of religion".
Embryonic leaves. Adaptive functions and taxonomic significance of cotyledons.
Asa Gray. Separation of sexes in U. S. trees.
Please cite as
Darwin Correspondence Project, “Letter no. 2116,” accessed on 25 May 2016, http://www.darwinproject.ac.uk/DCP-LETT-2116