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Darwin Correspondence Project

To George Bentham   18 December [1857]1

Down Bromley Kent

Dec. 18th

My dear Sir

I am very much obliged for answers which were just what I wanted & quite as explicit as I expected.—2 I have had already occasion to put in a salvo about doubtful identification of plants experimentised on.—3 Cucubalus viscosus & Italicus are extremely sterile together as might have been expected from what you say. All the other forms are extremely fertile, only one degree below normal fertility, & which one degree of lessened fertility may, I believe, be accounted for by the requisite manipulation &c.—

Anyhow Gærtner finds the same slight degree of lessened fertility (or rather a greater degree of infertility) between Cowslip & Primrose, & the Blue & Red common Anagallis—4

With very many thanks | Yours sincerely | C. Darwin


Dated by the relationship to the letters to George Bentham, 1 December [1857] and 15 December [1857], and the letter from George Bentham, [16 or 17 December 1857].
CD perhaps refers to his remarks concerning Karl Friedrich von Gärtner’s crosses of Datura stramonium and D. tatula that ‘it may be questioned … whether these forms should be considered as anything but varieties.’ (Natural selection, p. 404).
See Natural selection, p. 405.


Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.


Thanks GB for his answers [to 2184], which were as explicit as he expected. Cucubalus viscosus and italicus are extremely sterile together; all other forms extremely fertile. Other instances of infertility found by Gärtner.

Letter details

Letter no.
Charles Robert Darwin
George Bentham
Sent from
Source of text
Royal Botanic Gardens, Kew: Bentham, George letters: 700a
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 2189,” accessed on 22 September 2020,

Also published in The Correspondence of Charles Darwin, vol. 6