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Darwin Correspondence Project

To Hermann Müller   16 August [1867]1

Down, Bromley, Kent

Aug: 16.

Dear Sir

Ich bin Ihnen für Ihren höchst interessanten Brief sehr verbunden, aber es macht mir Sorge, dass Sie sich so viele Arbeit gemacht haben, mich zu verpflichten. … Sie theilen offenbar Ihres Bruders wundervolle Beobachstungsgabe, sowie seine Fertigkeit, sich englisch auszudrücken und seine Geschicklichkeit im Zeichnen.Ich hoffe, dass Sie Ihre excellente Beschreibung veröffentlichen werden. I was made aware by Prof. Asa Gray (either in a paper in the Amer. Journal of Science or in a letter) of my error with respect to Cypripedium.2 By an odd chance I put an Andrena into the labellum, and saw what you describe as naturally taking place.3 Ich kann nicht umhin, ein wenig an der Vergiftung der Bienen zu zweifeln, da es die Uerberführung des Pollens von Pflanze zu Pflanze durchkreuzen würde Bienen sterben, wenn sie stark angestrengt werden, bald an Erschöpfung. Der grosse Robert Brown behauptetindessin, dass der Nektar der Aslepias Bienen vergifte, und das unterstützt Ihre Ansicht. Sie erwähnen nicht der wohlangepassten Einwärtskrümmung des Randes der Lippenöffnung, welche die Insekten verhindert, herauszukriechen.

Ihre Beobachtungen an Epipactis erscheinen mir noch werthvoller. E. viridiflora scheint in demselben Falle wie Cephalanthera zu sein, aber man kann von dem Vorhandensein des Nektars daselbst schliessen, dass Insekten gelegentlich Pollen von Pflanze zu Pflanze führen. Könnten Sie nicht mit Anwendung des Pollens einer verschiedenen Pflanze und andererseits ihres eigenen experimentiren, und den Inhalt der Kapseln vergleichen? I do not doubt that this species is generally self-fertilized; and I am aware that I erred in supposing that this happened to so few species.4 Neottia nidus avis is often self-fertilized.5 Epipactis latifolia I find is always fertilized by wasps (vespa)6 — — — —

Yours very faithfully | Charles Darwin

Footnotes

The year is established by the reference, in the letter to Fritz Müller, 15 August [1867], to a letter from Hermann Müller containing observations on the fertilisation of orchids. Hermann began his work on orchids in the summer of 1867 (Möller ed. 1915–21, 2: 111).
In Orchids, pp. 274–5, CD had speculated on the means by which flowers of Cypripedium might be pollinated, concluding that an insect would have to insert its proboscis through one of two small openings above the lateral anthers. Gray concluded, from observations of American species of Cypripedium, that an insect would enter a flower through the large opening on the dorsal surface of the flower, then crawl out through one of the small openings above the anthers (see Correspondence vol. 10, letter to Asa Gray, 10–20 June [1862] and n. 16). Gray later published his observations in the American Journal of Science and Arts (A. Gray 1862).
In Orchids 2d ed., pp. 230–1, CD described his experiment with a small bee of the genus Adrena and referred to the observations of Gray and Müller (see also Correspondence vol. 11, letter to Asa Gray, 20 April [1863]). In the published version of his observations on Westphalian orchids, Müller described the pollination of Cypripedium calceolum, noting that the bee’s path through the flower necessitated its touching the stigma before the anthers, thus ensuring cross-fertilisation (H. Müller 1868, pp. 1–3).
The reference is probably to Müller’s observations on Epipactis viridiflora (see H. Müller 1868, pp. 7–10, and Orchids 2d ed., pp. 102–3). Müller observed that the flower lacked a rostellum, which in most orchids separates the anther from the fertile stigma, and so was easily self-pollinated. In Orchids, p. 358, CD had concluded that self-fertilisation in orchids was a ‘rare event’, but in the second edition he modified his view, acknowledging that some species were ‘regularly or often self-fertilised’ (Orchids 2d ed., p. 290).
In Orchids 2d ed., p. 290, CD included Neottia nidus-avis among those species capable of self-pollination, but more often pollinated by insects.
In Orchids 2d ed., pp. 101–2, CD noted that wasps were the only insects he had seen visiting Epipactis latifolia. Müller cited CD’s letter informing him of this fact in his paper on Westphalian orchids (H. Müller 1868, p. 12).

Summary

Made aware by Asa Gray of error with respect to Cypripedium. Does not doubt it is self-fertilised.

Letter details

Letter no.
DCP-LETT-5608
From
Darwin, C. R.
To
Müller, H. L. H.
Sent from
Down
Source of text
DAR 146: 429, Krause 1884
Physical description
1p inc

Please cite as

Darwin Correspondence Project, “Letter no. 5608,” accessed on 8 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-5608

letter