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Darwin Correspondence Project

To John Denny   14 July [1872]1

July 14th

Dr. Denny

Dear Sir

I am much obliged for your le. & present of the Florist.—2 You have been scrupulous in your manipulation & memoranda;3 but I am surprised that you have not protected as it appears the flowers from insects. I have found this indispensable in most of the [various] experiments wh. I have made during last 5 year.— These have been made for a distinct purpose from yours, & varieties have been avoided, & when employed no record was kept of the transmittance of character from the parents, in this I grieve to say I cannot aid you.—4 Before long a tr. of Gs. work will be published by Ray Soc.5 He is as emphatic as you are but in an opposite direction; viz that there is no difference in power of transfer by the f & m.; but he made his [illeg] experiments on distinct species, in which difference of constitution wd not probably come into play.—

As you have found out that the D. of Cornwall &c is fertile with its own pollen,6 & with that of some other varieties, when it is sterile with other vars, you have made in my opinion a remarkable discovery. I assume that the four experimented on are vars. ie not different in a state of nature, & that you have made many trials.—7 This discovery will, however, interest only a few of the more philosophical naturalists; & will I feel sure be easily lost to science, if published only in Hort. Journ. & without in much fuller detail than that given in the G. Chronicle.—8

Permit me, therefore, to urge on you to draw up a full account,— giving names of vars. (which were sterile with the D. of Cornwall &c) & reason for believing that they are vars— the number of trials made, both on the male & fem side &c—& send the account to some Botanical Journal. or Soc.— The Linnean Soc wd be the most appropriate; & your paper wd then be sent on to all the Scientific Soc. of Europe.—9 I shd be glad to aid in draw attention to it by a letter to Nature.10 If you will do this it wd be advisable perhaps I think to begin your paper by stating that you had discovered or raised, (as the case may be) vars of Pelargonium which were fertile with their own pollen &c &c &c, — & in so far partook of the character of true & distinct species—

It wd further be well to give full details about the converse case of the Ivy-leaved P., in which a var has assumed an abnormal degree of fertility.—11 In my Var. under Dom Vol. 2. p. 108 you will find an account of the sole [acknowledged] case, ever recorded in Nicotiana.—12

I hope that you will excuse the familiarity with which I have written to you & I remain— | C. D.


The year is established by the relationship between this letter and the letter from John Denny, 12 July 1872.
Denny had sent CD the issues of the Florist containing Denny 1872b (see letter from John Denny, 12 July 1872 and n. 5). CD later cited this paper in Cross and self fertilisation, p. 142.
In Denny 1872b, Denny described the methods of keeping written records as well as the tools required when cross-breeding pelargoniums by artificial fertilisation.
CD had suggested that the Ray Society translate Gärtner 1849 (see Correspondence vol. 12, letter to Ray Society, [before 4 November 1864]). Although the Ray Society minutes for 3 February 1865 record a resolution by the Council to employ a translator for Gärtner 1849, the work was never undertaken (see Curle 1954, p. 26).
For a brief account of the crosses Denny attempted with the pelagonium varieties ‘Surpasse Beauté de Suresnes’ and ‘Duke of Cornwall’, see Denny 1872b, p. 52.
Denny’s paper ‘The relative influence of parentage in flowering plants’ had been published in the Gardeners’ Chronicle (Denny 1872a). It was published again, with no revisions, in the Journal of Horticulture on 11 July (Denny 1872c) and in the Journal of the Royal Horticultural Society of London (Denny 1872d).
There is no paper by Denny in the Journal of the Linnean Society (Botany), nor is there any record of one having been read to the society.
In the event, Denny did not publish a fuller account of his experiments.
Denny had referred to this variety of ivy-leaved pelargonium as Peltatum elegans. See letter to John Denny, 9 July 1872 and n. 2.
In Variation 2: 108, CD described experiments by Joseph Gottlieb Kölreuter that showed that when five varieties of common tobacco (Nicotiana tabacum) were crossed with one another the offspring were as fertile as their parents, but when these five varieties were crossed with a different species, N. glutinosa, the resulting hybrids were ‘very sterile’ in four of the varieties but less so in the fifth, var. perennis. CD concluded that this showed that the ‘sexual capacity of this one variety [had] certainly been in some degree modified, so as to approach in nature that of N. glutinosa’ (ibid., pp. 108–9). For the value CD placed on these experiments, see also Correspondence vol. 10, letter to T. H. Huxley, 18 December [1862].


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 28 vols to date. Cambridge: Cambridge University Press. 1985–.

Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.

Curle, Richard. 1954. The Ray Society: a bibliographical history. London: Ray Society.

Gärtner, Karl Friedrich von. 1849. Versuche und Beobachtungen über die Bastarderzeugung im Pflanzenreich. Mit Hinweisung auf die ähnlichen Erscheinungen im Thierreiche, ganz umgearbeitete und sehr vermehrte Ausgabe der von der Königlich holländischen Akademie der Wissenschaften. Stuttgart: E. Schweizerbart.

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


Discusses JD’s crossing experiments with Pelargonium; notes that his conclusions on male prepotence oppose those of Gärtner. Suggests that his observations on differences in fertility of certain varieties of Pelargonium crossed with certain other varieties be communicated to the Linnean Society.

Letter details

Letter no.
Charles Robert Darwin
John Denny
Sent from
Source of text
DAR 96: 114–15
Physical description
AdraftS 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 8410,” accessed on 24 May 2022,

Also published in The Correspondence of Charles Darwin, vol. 20