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Darwin Correspondence Project

From Hermann Müller   10 June 1873


June 10 1873.

My dear Sir

Your letter has been a great pleasure to me by your consent to the last part of my book and by your remark that you have arrived on many points on the same conclusions that I have done.1 The book you are now about to write will indeed be of the highest interest to me and probably will decide in a great measure my further working.2

The same day I received your note on Viola tricolor3 I had occasion to observe some fertilisers of it, namely Apis mellifica L. ♀ repeatedly repeatedly, Bombus hortorum, B. Rajellus, Pieris rapae and napi, Polyommatus sp, and Rhingia rostrata, also this repeatedly sucking.4

Of the two forms of the wild Viola tricolor the inconscpicuous one self fertilises itself regularly although the flowers wither very slowly when not fertilised by the pollen of other flowers, and I have now collected seed of self-fertilised flowers. The other form with greater and more remarkably coloured flowers, blowing since several weeks in my garden under a net seems not to self fertilise itself; hitherto at least not a single flower has set a capsule.5

The observation of Mr Riley on a small moth fertilising a Yucca, you have had the kindness to acquaint me with, is a very singular and interesting one.6

I am much obliged to you also for your note on the book of Dr. F. G. Kurr which indeed is quite unknown to me. Unfortunately the publishing house of Henne has gone to ruin and the book of Dr Kurr is no more saleable.7

Enclosed I return to you the article of Mr Bennet you have had the kindness to send me, the Editor of Nature having been so complaisant as to send me the number containing it.8 Henceforth I will receive regularly the “Nature” for having promised to the Editor to afford to him some articles.

The last days I have examined some other grass-flowers, also that of Glyceria fluitans, but I have not yet succeeded to find drops of nectar. The two petala however are as succulent as in Poa annua9

Believe me. | yours very sincerely | H. Müller.

CD annotations

1.1 Your letter … working. 1.5] crossed blue crayon
2.1 The] opening square bracket blue crayon
2.2 namely … sucking. 2.4] scored blue crayon
2.2 Apis mellifica] underl blue crayon
2.2 Bombus hortorum 2.3] underl blue crayon
4.1 The observation … send me, 6.2] crossed blue crayon


CD had commented on Befruchtung der Blumen (Fertilisation of flowers; H. Müller 1873) in his letter to Hermann Müller, 30 May 1873.
Müller refers to Cross and self fertilisation.
CD’s note has not been found, but see the letter from Hermann Müller, 27 May 1873 and n. 1. Müller had sent information on his own experiments with Viola tricolor in his letter to CD of 19 May 1873.
Apis mellifica is now A. mellifera, the honey-bee. Bombus hortorum is the garden humblebee. Bombus rajellus is now B. ruderarius, the red-shanked bumblebee or carder-bee. Pieris rapae is the small white butterfly; P. napi is the green-veined white. Polyommatus is a genus of butterflies in the family Lycaenidae. Rhingia rostrata is a species of hoverfly.
On Viola tricolor, see the letter from Hermann Müller, 19 May 1873, and H. Müller 1873, p. 145.
Charles Valentine Riley had described a new species of moth (Pronuba yuccasella, now Tegeticula yuccasella, the yucca moth) that fed exclusively on the nectar of the yucca, and mutual adaptations of the insect and flower that ensured cross-pollination (Riley 1869–77, 5: 150–60). CD’s annotated copy is the Darwin Library–CUL (see Marginalia 1: 711–12). CD included Riley’s observations in Cross and self fertilisation, p. 418. For a modern commentary on Riley’s work, see Baker 1986.
CD’s copy of Johann Gottlob von Kurr’s Untersuchungen über die Bedeutung der Nektarien in den Blumen (Investigation of the significance of the nectaries of flowers; Kurr 1833) is extensively annotated, with a separate abstract of the book (see Marginalia 1: 472–4). The publisher was Friedrich Henne’sche Buchhandlung of Stuttgart.
See letter from Hermann Müller, 19 May 1873. Müller was interested in an article by Alfred William Bennett on fertilisation in Viola tricolor (A. W. Bennett 1873a). The editor of Nature was Joseph Norman Lockyer. Müller contributed many articles to Nature between 1874 and 1883.
Glyceria fluitans is an aquatic perennial grass (see letter from Hermann Müller, 27 May 1873 and n. 1). Poa annua is a meadow-grass.


Baker, Herbert G. 1986. Yuccas and Yucca moths–a historical commentary. Annals of the Missouri Botanical Garden 73: 556–64.

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

Kurr, Johann Gottlob von. 1833. Untersuchungen über die Bedeutung der Nektarien in den Blumen: auf eigene Beobachtungen und Versuche gegründet. Stuttgart: Henneschen Buchhandlung.

Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.

Müller, Hermann. 1873. Die Befruchtung der Blumen durch Insekten und die gegenseitigen Anpassungen beider. Ein Beitrag zur Erkenntniss des ursächlichen Zusammenhanges in der organischen Natur. Leipzig: Wilhelm Engelmann.

Riley, Charles Valentine. 1869–77. Annual reports on the noxious, beneficial, and other, insects of the State of Missouri. Jefferson City, Mo.: Regan & Edwards, public printer [and others].


Reports on insects fertilising Viola tricolor and on the fertilisation of the two wild forms [see Cross and self-fertilisation, p. 124 n., 125].

Letter details

Letter no.
Heinrich Ludwig Hermann (Hermann) Müller
Charles Robert Darwin
Sent from
Source of text
DAR 77: 154–5
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 8941,” accessed on 6 March 2021,

Also published in The Correspondence of Charles Darwin, vol. 21