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Darwin Correspondence Project

To Asa Gray   21 July [1855]

Down Farnborough Kent

July 21st.—

My dear Dr. Gray

I must write one line to thank you for your letter of the 30th ulto., & for the extremely kind manner in which you have acceded to my request (which I assure you I long hesitated whether I would make) about marking the close species. I do not quite understand from Hooker’s note, whether the sheets have arrived, but I fancy not; but I shall hear again in two or three days. Hooker read over your letter, & seems to have been as much struck with it as I have been,—as showing in a most striking manner the geographical affinities of species, & the difficulty of ascertaining what are species.— Your discussion on connecting & separating forms seems to me so philosophical, that I much hope that someday you will be as good as your word & write an “Essay on Species”.1

I hope, also, before end of year to hear that you have found time to write on the geographical distribution of the U.S. plants;2 & if my letter caused you to do this some year or two before you otherwise would have done it, I shall congratulate myself in private, at having done good Botanical work.

Pray believe me with cordial thanks | Yours very sincerely | Charles Darwin

Some of my immersed seeds have come up after 82 & 85 days immersion, viz Radishes Beet, Atriplex, Capsicum, Oats, Cucurbita, Rhubarb, Lettuce, Carrotts, Celery, & Onions.—3


Gray, Asa. 1856–7. Statistics of the flora of the northern United States. American Journal of Science and Arts 2d ser. 22: 204–32; 23: 62–84, 369–403.


Geographical distribution. "Close" species. Hopes AG will write an essay on species.

Letter details

Letter no.
Charles Robert Darwin
Asa Gray
Sent from
Source of text
Archives of the Gray Herbarium, Harvard University (3)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 1725,” accessed on 14 April 2021,

Also published in The Correspondence of Charles Darwin, vol. 5