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Darwin Correspondence Project

From Hermann Müller   5 July 1878


July 5, 1878.

My dear Sir!

Annexed I send you some seeds which my brother Fritz has collected for you and which two of his daughters arriving here from Brazil have brought along with.1

Last year I have fertilised in different ways the two forms of Viola tricolor: a) the form with small yellowish flowers (var arvensis) b) the form with large gay-coloured flowers.2 The descendants of them are now blooming in my garden. The results are as follows:

1) a) crossed with pollen of b). The flowers of the descendants are equal in size and colour to those of a). so that I am doubtful whether cross fertilisation has been of effect—self fertilisation always very early taking place

2) a) crossed with pollen of a) from a distant locality

The same result as in 1)

3) b) crossed with pollen of a) The flowers of the descendants are in colour equal to those of b) but in size much smaller, intermediate between a) and b)

4) b) crossed with own pollen Only 6 descendants have been obtained. Flowers in colour like those of the parents, in size much smaller, even smaller than in 3).

The fertilisation of a) offers great difficulty, the cavity of the stigma often being filled with pollen grains immediately after the opening of the flower. I have attempted to remove them but some ones may easily have remained.

Unfortunately this year I am too much overwhelmed with work to continue the trials with Viola tricolor, but certainly recommence them sometime and continue through some years.

With the most sincere respects | yours | very sincerely | H Müller

CD annotations

Top of letter: ‘Ophrys Your paper’3 pencil


Fritz Müller’s daughters Anna and Emma had travelled to Germany in May 1878 (West 2016, p. 153). The seeds have not been identified but may have included seeds of Cassia (see letter to Fritz Müller, 24 July 1878).
Viola tricolor is heart’s-ease; Viola tricolor var. arvensis is a synonym of Viola arvensis, the field pansy. CD had advised Müller on crossing experiments with V. tricolor and other plants with two different kinds of flowers in a letter that has not been found (see Correspondence vol. 25, letter from Hermann Müller, 2 April 1877 and n. 1).
CD’s annotations are probably notes for his reply, which has not been found. Ophrys is a genus of terrestrial orchids; CD had made observations on fertilisation in several species (see Orchids). The first part of a paper by Müller, ‘Die Insekten als unbewußte Blumenzüchter’ (Insects as unconscious flower breeders; H. Müller 1878), was published in Kosmos, July 1878; the concluding parts were published in the August and September issues. CD’s annotated copy is in his collection of unbound journals in the Darwin Archive–CUL. Müller had referred to Ophrys muscifera (a synonym of O. insectifera subsp. insectifera, the fly orchid) as typifying a class of flowers that lured insects by means of deception without offering a nectar or pollen reward (H. Müller 1878, pp. 335–6).


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

Müller, Hermann. 1878. Die Insekten als unbewußte Blumenzüchter. Kosmos 3: 314–37; 403–26; 476–99.

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.

West, David A. 2016. Darwin’s man in Brazil: the evolving science of Fritz Müller. Gainsville, Fla.: University Press of Florida.


Reports results of crosses between the two forms of Viola tricolor: 1. Female small flower crossed with male large flower yields all small flowers (cleistogamous self-fertilisation suspected); 2. Male small flower crossed with female large yields intermediate flowers; 3. Large flower crossed with large flower yields self-sterility symptoms.

Letter details

Letter no.
Heinrich Ludwig Hermann (Hermann) Müller
Charles Robert Darwin
Sent from
Source of text
DAR 171: 310
Physical description
ALS 2pp †

Please cite as

Darwin Correspondence Project, “Letter no. 11592,” accessed on 2 June 2023,