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Darwin Correspondence Project

To George Bentham   22 April 1868

Down. | Bromley. | Kent. S.E.

Ap 22nd. 1868

My dear Mr. Bentham

I have been extremely much pleased by your letter, and I take it as a very great compliment that you should have written to me at such length. I have been much interested by many of your details, though I regret greatly that I did not know your facts about the varieties of the ass, kidney-bean & artichoke before I published. Many thanks also for your references, but it is a great drawback to me that I have not strength to read nearly as much as I should wish.1

I am glad to hear what you say about wheat, though I did not know that you believed it to be a descendant of Ægilops.2

I am not at all surprised that you cannot digest Pangenesis; it is enough to give any one an indigestion; but to my mind the idea has been an immense relief, as I could not endure to keep so many large classes of facts all floating loose in my mind without some thread of connection to tie them together in a tangible method.3

With respect to the men who have recently written on the crossing of Plants, I can at present remember only Hildebrand   Fritz Müller   Delpino & G. Henslow; but I think there are others.4 I feel sure that Hildebrand’s is a very good observer, for I have read all his papers & during the last 20 years I have made unpublished observations on many of the plants which he describes. Most of the criticisms which I sometimes meet with in French works against the frequency of crossing I am certain are the result of mere ignorance.5 I have never hitherto found the rule to fail that when an author describes the structure of a flower as a specially adapted for self-fertilization, it is really adapted for crossing. The Fumariaceæ offer a good instance of this, & Treviranus threw this order at my teeth, but in Corydalis Hildebrand shows how utterly false the idea of self fertilisation is.6 This author’s paper on Salvia is really worth reading & I have observed some species & know that he is accurate.7 Judging from a long review in the Bot. Zeitung & from what I know of some of the plants I believe Delpino’s article especially on the Apocyneæ is excellent: but I cannot read Italian.8

Perhaps you would like just to glance at such pamphlets as I can lay my hand on, & therefore I will send them as if you do not care to see them, you can return them at once; & this will cause you less trouble than writing to say you do not care to see them.

With respect to the Primulas the one point about which I feel positive is that the Bardfield & common oxslips are fundamentally distinct plants, & that the common oxslip is a sterile hybrid.9 I have never heard of the common oxslip being found in great abundance anywhere; & some amount of difference in number might depend on so small a circumstance as the presence of some moth which habitually sucked the primrose & cowslip.

To return to the subject of crossing; I am experimenting on a very large scale on the difference in power of growth between plants raised from self fertilised & crossed seeds; and it is no exaggeration to say that the difference in growth & vigour is sometimes truly wonderful.10 Lyell, Huxley & Hooker11 have seen some of my plants & been astonished; & I should much like to show them to you. I always supposed until lately that no evil effects wd be visible until after several generations of self fertilisation; but now I see that one generation sometimes suffices; & the existence of dimorphic plants & all the wonderful contrivances of orchids are quite intelligible to me.

With cordial thanks for your letter which has pleased me greatly | Your’s very sincerely | Charles Darwin

P.S. I heard some time ago from Dr. Hildebrand that he had succeeded in making a graft-hybrid, & I inserted this in the Reprint of my last book.— He will publish an account in Bot. Zeitung.12 Tubers produced from buds of one kind inserted into a distinct kind, were hybridised or intermediate in characters. This seems to me a most important fact for any theory of generation, & supports Pangenesis.13 I am a firm believer & worshipper of my God Pan, & am convinced that all hereticks some day will be converted; but you hereticks are at present terribly numerous.—


In his letter of [before 22 April 1868], Bentham had asked for names of persons pursuing lines of research following on from CD’s. CD refers to Friedrich Hildebrand, Fritz Müller, Federico Delpino, and George Henslow.
In his letter of [before 22 April 1868], Bentham referred to French criticisms of Hildebrand’s observations on cross-fertilisation. No French authors were referred to by name.
Corydalis (fumewort) was a member of the order Fumariaceae. This order roughly corresponds to the modern family of the same name. Ludolph Christian Treviranus had written critically about CD’s thesis that most flowers had special adaptations to ensure cross-fertilisation (see Treviranus 1861, 1863a, 1863b, and 1863c); however, no specific mention of the Fumariaciae has been found. CD began experimental work on fumitories after receiving a letter from Asa Gray, who claimed that Fumariaceae were perpetually self-fertilised (see Correspondence vol. 6, letter from Asa Gray, 7 July 1857, and letter to Asa Gray, 29 November [1857]). CD’s botanical notes on Fumariaceae, dated from 1857 to 1863, are in DAR 76: B13–21. CD also refers to Hildebrand’s papers on Corydalis cava (Hildebrand 1866 and 1866–7).
CD refers to Hildebrand’s paper on insect-aided fertilisation of Salvia species (Hildebrand 1866a).
CD refers to a three-part review of Delpino’s monograph on the structure of flowers as an aid to cross-fertilisation (Delpino 1867b) by Hildebrand (Hildebrand 1867b).
See letter from George Bentham, [before 22 April 1868] and n. 20. CD refers to Primula elatior (the Bardfield oxlip), and to P. veris x P. vulgaris (the common oxlip).
CD began his experiments on the relative growth of plants raised from seeds of self-fertilised or cross-fertilised plants in 1866 (see Correspondence vol. 14, letter to Asa Gray, 10 September [1866] and n. 13). The results were eventually published in Cross and self fertilisation.
Charles Lyell, Thomas Henry Huxley, and Joseph Dalton Hooker.
See letter from Friedrich Hildebrand, 2 January 1868 and n. 3. Hildebrand published his results in the 15 May 1868 issue of Botanische Zeitung (Hildebrand 1868a). CD’s annotated copy of the article is in the Darwin Pamphlet Collection–CUL.
For CD’s belief in the importance of graft hybrids for his hypothesis of pangenesis, see Variation 2: 364–5.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Treviranus, Ludolph Christian. 1861. [Review of J. D. Hooker’s Flora Tasmaniæ.] Botanische Zeitung 19: 133–5, 142–4.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Is not surprised that GB cannot digest Pangenesis, but it has been an immense relief to CD in tying together large classes of facts.

Sends names of men writing on crossing of plants. Criticises some French observations. Praises Hildebrand and Federico Delpino.

Sends pamphlets.

CD is experimenting on a large scale on difference in plants raised from self-fertilised and crossed seeds.

F. Hildebrand has produced a graft-hybrid which seems to lend important support to Pangenesis.

Letter details

Letter no.
Charles Robert Darwin
George Bentham
Sent from
Source of text
Royal Botanic Gardens, Kew (GEB/1/3 ff. 703–4, 706)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6138,” accessed on 18 November 2019,

Also published in The Correspondence of Charles Darwin, vol. 16