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Darwin Correspondence Project

From Hermann Crüger   23 April 1863


23 April | 63.

Dear Sir

I have received your kind note of 18 March.1 I shall gladly make the observations you speak of & report when I shall have done so. I have continued to observe the bees which frequent the Heteronoma spoken of in my last.2 There are two bees which visit this flower, one is a large spec, about the size of our European bee, but somewhat plumper, of a greyish color. The visitors come only for pollen, which they regularly get from the anthers by pressing them between their mandibles beginning from the base of the anther until they arrive at the top, when the clump of pollen is transferred in the usual manner to the legs. The bee takes its seat on the top of the bundles of anthers, of which in this plant there are two. The shorter of the stamens surround the pistil, & the pollen comes so in contact with the stigma by the instrumentality of the bee.

I have repeatedly examined the stamens & anthers of these flowers & could not find any the slightest wound or puncture, nor can I find any nectar. The other bee which visits these flowers is a small golden-green one, rather lively & difficult of approach, but I think I may affirm it also comes only for pollen. I shall send you some sketches, when I have a few more facts connected with this family.3

I am glad to see that my notes on orchideae interested you.4 As I told you before, your book on Orchids has produced some doubts on the correctness of what I had noted down & partly sketched5   I shall therefore begin the work again & send you notes, drawings, & specimens for your autopsy. The substance the humble-bees are so eager after in the Catasetum is some secretion in or near the inner surface of the labellum, but I must investigate this also anew.6 For this purpose I have collected a lot of Catasetum tridentatum, & as soon as they flower I shall begin again. With regard to the orchids which rarely or never open, I must say that I have had a short time ago one of the Epidendrums of Lindleys folia Orchs.— No 60–68. (perhaps the very No 65. of which Ldl. says “the flowers never expand”) fully open.7 These have not set fruit, while commonly I do not remember to have noticed a flower which was not followed by fruit. The seeds of these plants I have examined but could not discover any difference between them & others.8 I have never been able to make a single Orchid germinate here, but I shall try it again. Some species germinate here abundantly by themselves such as Oncidium luridum, ampliatum, Epidendrum rigidum, ramosum, fragrans.9

I have noted you other desiderata & shall attend to them. With regard to Ficus, I have spent some time on them when I occupied myself with the fecundation of plants. A short account of my studies on Ficus you will find in the Botanische Zeitung 1851, p 60.10 I am firmly convinced that without insects Figs will rarely or never give seeds, but I shall try the experiment you suggest.—11 I have your last two works, Origin of Species & the Orchids, & have read the Journal of researches often, if you send me the latter I shall be delighted to accept it as a keepsake from its celebrated author.—12 I believe I wrote in my last, that this is our dry season & therefore little to be found in flower. The rains begin in the middle of May or in June. As soon as the several plants begin to flower you speak of I shall observe them carefully. I intend to observe Cassias & Mimosas as also some Solanums. Of Begonias we have only 4 species, three of them common enough about here, the fourth grows only at a certain elevation.13 I am inclined to believe that they are fertilised by insects as foreigners even from neighbouring places produce no seed. I know that this is a dangerous test, but it is remarkable how many exotics while flowering most abundantly are shy seeders. Of course other explanations may be given, if a plant f[or] instance came from southern tropical countries, where the seasons are reversed some influence might be deduced from this circumstance. But this would not apply to cases where a plant only transplanted from Jamaica would not seed here. I do not remember a Vanda or any other Indian or African Orchid setting a single seed-vessel. And still insects commit sometimes errors, as it is perfectly possible that an humble bee may alight on a Dendrobium taking it for something else of this country.

If you have any thing else to be done in the sake of science & progress I repeat that I am at your command.

Believe me | dear Sir | very sincerely yours | H Crüger

CD annotations

3.1 I am … autopsy. 3.4] crossed ink
3.4 bees are … anew. 3.6] ‘The substance the humble- | orchids’ added ink
4.1 With … Solanums. 4.11] crossed ink
4.15 I know that … seeders. 4.16] double scored ink
4.20 I do … seed-vessel. 4.21] double scored ink
Top of letter: ‘Dr Hermann Cruger’ ink
End of letter: ‘Sporting Plants.’14 ink, del ink; ‘April 23d. 1863’ ink


CD’s letter to Crüger has not been found.
CD had hypothesised that flies or small wasps might puncture the horns on the stamens of Melastomataceae in order to collect the fluid within (see letter to Asa Gray, 19 January [1863]).
CD’s letter has not been found, but see the letter from Hermann Crüger, 23 February 1863.
Crüger refers to Orchids, and to his observations of the supposedly distinct orchid species Catasetum tridentatum and Myanthus barbatus (see letter from Hermann Crüger, 23 February 1863 and n. 6).
In ‘Fertilization of orchids’, p. 154 (Collected papers 2: 151), CD reported that Crüger had sent him specimens of bees that he had seen ‘gnawing the inside of the labellum’. See Correspondence vol. 12, letter from Hermann Crüger, 21 January 1864, and Crüger 1864.
Crüger refers to the section on Epidendrums in Lindley 1852–5. Numbers 60–8 are descriptions of nine species; number 65 is a description of Epidendrum gravidum.
See Crüger 1864, Orchids 2d ed., pp. 147–8, and letter from Hermann Crüger, 23 February 1863 and n. 5. CD mentioned Crüger’s self-pollinating orchids in his letter to the Journal of Horticulture, [31 March 1863]; he also discussed them with John Scott (see letter from John Scott, [1–11] April [1863]).
CD was interested in attempting to germinate orchid seed (see following letter and n. 5), and had probably asked Crüger for information on the subject in the letter of 18 March 1863 that is now missing (see n. 1, above).
Crüger 1851.
CD evidently described an experiment in his missing letter to Crüger of 18 March 1863 (see n. 1, above), but see also Correspondence vol. 12, letter from Hermann Crüger, 21 January 1864.
Crüger refers to Origin, Orchids, and Journal of researches. See letter to Hermann Crüger, 25 May [1863].
CD had suggested crossing experiments on begonias to John Scott (see Correspondence vol. 10, letter to John Scott, 19 December [1862]), and may have asked Crüger about the fertility of begonias in Trinidad (see n. 1, above). For experimental notes on begonias dated 19 March and 6 April 1863, see DAR 49: 83.
In his letter to Crüger of 25 May [1863], CD asked whether Crüger had any information on ‘sports’, or what CD called ‘bud-variations’. For CD’s interest in bud-variations, see letter to Asa Gray, 2 January [1863] and n. 18.


Observations on Catasetum.

Figs require insects in order to set seed.

Letter details

Letter no.
Hermann Crüger
Charles Robert Darwin
Sent from
Source of text
DAR 161: 276, DAR 205.8: 68 (Letters)
Physical description
6pp †

Please cite as

Darwin Correspondence Project, “Letter no. 4124,” accessed on 25 August 2019,

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