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Darwin Correspondence Project

To Friedrich Hildebrand   10 August [1871]1

Down Beckenham | Kent [Haredene, Albury, Guildford]

Aug 10

My dear Sir

Owing to other occupations I have only just read your very interesting paper on Oxalis. I am exceedingly pleased to see it published, as the analogous case of Lythrum has always appeared to me so wonderful that I expected hardly any one to believe the facts until they were confirmed.2

I have made some experiments, but not so full as yours, on a S. African Oxalis, & the results agree with yours, as far as I remember. I cannot look at my MS. as I am writing this away from home.3

My health is so indifferent that I do not know whether I shall ever have time to publish my observations on this Oxalis & some dimorphic plants.4 I wish yr idea about the character of the progeny of the legitimate unions of trimorphic plants had occurred to me; for assuredly I would have crossed the same 2 forms of Lythrum for several successive generations & have observed the character of the progeny.5 I think this wd be well worth your while in the case of Oxalis. Should you ever have the opportunity I earnestly hope that you will attend to the degree of fertility of any illegitimate plants in comparison with legitimate, cultivated under the same conditions. I believe that at some future day the importance of these results will be recognised; though as yet you are the sole botanist who, as far as I know, has noticed my paper.

With very sincere respect believe me my dear Sir | yours faithfully | Ch. Darwin

P.S. Very many thanks for the list of seeds, which I will remember; but I do not want any at present.6

What you say about my works suggesting new lines of research, I consider one of the greatest compliments you cd possibly pay me—7


The year is established by the reference to Hildebrand 1871 (see n. 2, below), and by the relationship between this letter and the letter from Friedrich Hildebrand, 5 February 1872 (Correspondence vol. 20).
In his paper ‘Experimente und Beobachtungen an einigen trimorphen Oxalis-Arten’ (Experiments and observations on some trimorphic Oxalis species; Hildebrand 1871), Hildebrand described crossing experiments with three distinct sexual forms of Oxalis, demonstrating that each form was more fertile with pollen from either of the other two forms than with pollen from a plant of the same form. Hildebrand had reported his findings to CD the previous year (Correspondence vol. 18, letter from Friedrich Hildebrand, 16 July 1870). CD had described the similar case of Lythrum in 1864 (‘Three forms of Lythrum salicaria; see also Correspondence vol. 12, especially Appendix III). CD’s annotated copy of Hildebrand 1871 is in the Darwin Pamphlet Collection–CUL.
CD’s notes on crossing experiments conducted on various species of Oxalis between 1862 and 1868 are in DAR 109: B3–27, B101. The only South African species was O. bowiei, earlier spelled ‘Bowei’ and sometimes referred to by CD as ‘Bowii’, the name given when he purchased it (see Correspondence vol. 14, letter to Gardeners’ Chronicle, [before 11 August 1866]). The Darwins stayed at Haredene from 28 July to 25 August 1871 (CD’s ‘Journal’ (Appendix II)).
CD published the results of his experiments on Oxalis speciosa and O. bowii in 1877, with an abstract of Hildebrand 1871, in Forms of flowers, pp. 169–83.
Hildebrand showed that in two trimorphic species of Oxalis (O. valdiviana and O. regnelli), crossing any two of the three forms produced offspring predominantly but not exclusively of the same two forms; however, those fertilised with pollen from a plant of the same form produced offspring exclusively of that form (Hildebrand 1871, p. 442; see also Forms of flowers, pp. 212–13). For CD’s work on Lythrum salicaria see ‘Three forms of Lythrum salicaria; see also Forms of flowers, p. 213.
Hildebrand had supplied CD with seeds for his experiments (see Correspondence vol. 18, letter to Friedrich Hildebrand, 4 July 1870, and letter from Friedrich Hildebrand, 16 July 1870). No more recent letter from Hildebrand offering to send seeds has been found.
This remark was possibly made in a lost letter. Hildebrand refers to CD’s work on Lythrum throughout his paper (Hildebrand 1871) but makes no such specific acknowledgment.


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

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

Hildebrand, Friedrich. 1871. Experimente und Beobachtungen an einigen trimorphen Oxalis-Arten. Botanische Zeitung 29: 415–25, 431–42.

‘Three forms of Lythrum salicaria’: On the sexual relations of the three forms of Lythrum salicaria. By Charles Darwin. [Read 16 June 1864.] Journal of the Linnean Society (Botany) 8 (1865): 169–96. [Collected papers 2: 106–31.]


Mentions experiments on Lythrum.

Thanks for list of seeds.

Letter details

Letter no.
Charles Robert Darwin
Friedrich Hermann Gustav (Friedrich) Hildebrand
Sent from
Haredene Down letterhead
Source of text
Klaus Groove (private collection); sold by Venator and Hanstein, Cologne (dealers), 16 March 2018
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 7902,” accessed on 24 January 2020,

Also published in The Correspondence of Charles Darwin, vol. 19