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Darwin Correspondence Project

From Roland Trimen   10, 13, and 18 October 1863

Colonial Office, | Cape Town.

10th. October, 1863.

My dear Sir,

I have today received your very welcome letter of August 27th.,1 with the paper on Linum, for which I am very thankful.2 I have read the paper with much interest, but have not yet thoroughly studied it. How very astonishing are the marked differences in individuals of one and the same species in the growth and position of the eminently important sexual organs: and, still more, the wonderful fact that the pollen of either form is wholly (or very nearly) ineffectual in fertilising an individual presenting the same modification. To me, the dimorphism presented by Linum and Oxalis seems more difficult to account for than the strangest Orchid modification,3 because of the extraordinary fact that the same great law in constant operation has produced exactly opposite structural modifications in different individuals of the same species,—and that not a plant with separated sexes. By what remarkable process are such conflicting results, so evenly balanced, of natural selection to be accounted for?

The very common White Oxalis (no. 1) of which I enclose a specimen is often pink or pink-tinged, and, like the yellow one I sent in my last,4 is dimorphic. I gathered 37 flowers at random here and there, and found on examination that in 10 only the stigmas were uppermost; in the remaining 27 the anthers held the superior position.

I was very much delighted to find two other species of Oxalis which are trimorphic. Of the first of these (unfortunately I have preserved no examples) I only gathered 13 flowers (they are white, with narrow crimson edgings to each petal, and, never opening widely, the crimson lines have a beautiful half-spiral effect);—

proportion of 3 forms as follows:

Stigmas lowermost, 3 The leaves of this

〃  central, 7 Oxalis are linear or

〃  uppermost, 3 nearly so.


The other, of which I enclose 2 specimens of each form, is pinkish-red, with a wide yellow centre (also a very common species). I found the following to be the relative proportion of the three forms:5

Stigmas lowermost, 21

〃  central, 12 No. 3.

〃  uppermost, 10


I am glad the “peach-puncturing” is likely to be of use, & hope that your renewed strength at Malvern will enable you to give publicity to the evidence it seems to afford in favour of the Moth agency in fertilising the “Scheinsaftblumen”.6

With regard to Cypripedium (though it is very likely Asa Gray may be right in his suggestion) I venture to observe that I don’t think your putting in a small bee quite a fair experiment in re the plant’s fertilisation, because it does not appear that the said bee would voluntarily have acted as he twice did under exceptional circumstances.7

I have read a good part of Bates’ book, and think it very good,8 especially his remarks on the universal predominance of an unmistakeable sylvan type in the whole fauna of Equatorial America.9 His remarks on Lepidoptera are especially interesting to me.10

13th .— By this mail I received a very kind and interesting letter from Mr. Bates,11 chiefly referring to a few observations I ventured to make on his striking & able paper on the Heliconidæ and their mimickers.12 I had some difficulty in regarding the Nymphalideous butterflies, with their more or less atrophied fore-legs, as the supreme types or highest forms of Lepidopterous life, but Mr. Bates has most simply explained it to me by the remark that it appears to him “that the more aerial a Lepidopteron becomes, the more perfect it is, and the atrophy of the legs is a sign of less terrestrial habits, &c.” He has kindly offered me a series of Amazonian Rhopalocera, in return for which I hope to supply some gaps in his South African representation of the group

By Mr. Adamson,13 the Chief Clerk in the Office where I serve, I have sent you (addressed to care of Mr. Stevens)14 a bottle of spirit in which are a few Orchid flowers in different stages of growth. I have a few more bottled for you, which I hope to have the pleasure of sending before long, although you warn me in your last letter that you have little hope of being able to work up the accumulation of new Orchid material.15 Still, in case you ever should have a little leisure, I should be sorry to have missed the chance of affording you some aid, be it ever so little.

I hope you will pardon me for asking you to do me the favour of posting the enclosed note to Mr. Bates. Under the altered postal arrangements, I find my English correspondence somewhat expensive, and yet I do not like to forego the convenience of the regularity ensured by the monthly line of Steamers16

This morning, and often recently, I have been trying to find some Oxalis seed, but without success. The plants of the yellow species I sent you are plentiful enough,— their flowers are all gone, but I can find no seeds. I found many flowerstalks, the ends of which were brown and shrivelled, from which ends it appeared as if the capsule & part of stalk immediately below it had wasted away. Is there anything unusual in the seeding of Oxalids, or am I merely unfortunate or stupid?

Is not the case of a mule casting a foal very rare? I believe I can furnish you with some authentic details of such a case which recently occurred in this Colony. The foal is now in the Museum,17 and is a weird-looking object enough. The sire of this still-born oddity is stated by the donor to have been a donkey. Layard has a letter containing particulars,18 of which I have no doubt I could send you a copy, if it would be of any use.

Wishing you renewed strength for the prosecution of your researches, | I remain, my dear Sir, | Yours very truly, | Roland Trimen.

P.S. (18th.)— I leave tomorrow on a week’s trip to a part of the country which I have not yet visited. I trust to fall in with some local forms of both Insects & Plants.

CD annotations

0.2 1863.] underl red crayon
1.1 I have … for? 1.13] crossed blue crayon
2.1 (No. 1)] underl blue crayon
3.14 No. 3.] underl red crayon
4.1 I am … circumstances. 5.5] crossed red crayon
4.1 I am … material. 8.6] crossed blue crayon
9.1 I hope … Plants. 13.2] crossed blue crayon


‘Two forms in species of Linum; for CD’s presentation list for this paper, see Correspondence vol.11, Appendix IV.
CD and Trimen had been discussing dimorphism in Oxalis and Linum. See letter from Roland Trimen, 16, 17, and 19 July 1863, and letters to Roland Trimen, 23 May [1863], and 27 August [1863] and nn. 3 and 6.
Trimen sent CD specimens and a sketch of dimorphic O. cernua (a synonym of O. pes-caprae, African wood-sorrel) with his letter of 16, 17, and 19 July 1863. The specimens Trimen mentions in this letter have not been found.
CD quoted Trimen’s observations in Forms of flowers, p. 169.
‘Scheinsaftblumen’ are sham nectar-producers, or flowers with false nectaries (Orchids, pp. 45–50). See letter from Roland Trimen, 16, 17 and 19 July 1863, and letter to Roland Trimen, 27 August [1863] and nn. 7 and 8. See also letter to [Gardeners’ Chronicle], [after 27 August 1863].
See letter to Roland Trimen, 27 August [1863] and nn. 12–13. These experiments led CD to revise his conclusions regarding pollination in Cypripedium (see ‘Fertilization of orchids’, pp. 155–6 (Collected papers 2: 152–3)).
Trimen refers to Henry Walter Bates’s The naturalist on the river Amazons (Bates 1863).
Presumably a reference to Bates 1863, 1: 48, 71–2, and 108.
Trimen was a specialist in Lepidoptera (DSAB).
L. Adamson was chief clerk in the Colonial Office at the Cape of Good Hope (Colonial Office list).
Samuel Stevens was a natural history agent at 24 Bloomsbury Street, London (List of the Linnean Society of London, Post Office London directory 1863). The specimens have not been found.
The rates of postage from Cape Town had probably increased considerably; the rates of postage for mail from London to Cape Town had doubled in April 1863 (British postal guide 1863). The official mail service from Cape Town was available monthly; mail could also be carried by private ship, but the availability of this means of transport was more uncertain (ibid.).
Trimen refers to the South African museum in Cape Town (see also n. 18, below).
The reference is to Edgar Leopold Layard who, in addition to his duties as a civil servant, was the founder and curator of the South African museum in Cape Town (DSAB, Modern English biography). Layard had corresponded with CD in 1856 (see Correspondence vol. 6).


Bates, Henry Walter. 1861. Contributions to an insect fauna of the Amazon valley. Lepidoptera: Heliconidæ. [Read 21 November 1861.] Transactions of the Linnean Society of London 23 (1860–2): 495–566.

Bates, Henry Walter. 1863. The naturalist on the River Amazons. A record of adventures, habits of animals, sketches of Brazilian and Indian life, and aspects of nature under the equator, during eleven years of travel. 2 vols. London: John Murray.

British postal guide: British postal guide; containing the chief public regulations of the Post Office with other information. London: Post Office [and others]. 1861–76.

Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

Colonial Office list: The Colonial Office list … or, general register of the colonial dependencies of Great Britain. London: Edward Stanford; Harrison & Sons. 1862–99.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

DSAB: Dictionary of South African biography. Edited by W. J. de Kock et al. 4 vols. Pretoria and Cape Town: Nasionale Boekhandel Beperk [and others]. 1968–81.

‘Fertilization of orchids’: Notes on the fertilization of orchids. By Charles Darwin. Annals and Magazine of Natural History 4th ser. 4 (1869): 141–59. [Collected papers 2: 138–56.]

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

List of the Linnean Society of London. London: [Linnean Society of London]. 1805–1939.

Modern English biography: Modern English biography, containing many thousand concise memoirs of persons who have died since the year 1850. By Frederick Boase. 3 vols. and supplement (3 vols.). Truro, Cornwall: the author. 1892–1921.

Orchids: On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. By Charles Darwin. London: John Murray. 1862.

Post Office London directory: Post-Office annual directory. … A list of the principal merchants, traders of eminence, &c. in the cities of London and Westminster, the borough of Southwark, and parts adjacent … general and special information relating to the Post Office. Post Office London directory. London: His Majesty’s Postmaster-General [and others]. 1802–1967.

‘Two forms in species of Linum’: On the existence of two forms, and on their reciprocal sexual relation, in several species of the genus Linum. By Charles Darwin. [Read 5 February 1863.] Journal of the Proceedings of the Linnean Society (Botany) 7 (1864): 69–83. [Collected papers 2: 93–105.]


Comments on CD’s paper on Linum [Collected papers 2: 93–105].

Sends specimens of dimorphic and trimorphic Oxalis.

Comments on H. W. Bates’s work [Naturalist on the river Amazons].

Letter details

Letter no.
Roland Trimen
Charles Robert Darwin
Sent from
Cape Town
Source of text
DAR 109: B122–3
Physical description
ALS 4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 4319,” accessed on 13 September 2023,

Also published in The Correspondence of Charles Darwin, vol. 11