From Hermann Müller   27 May 1873

Lippstadt,

May 27. 1873.

My dear Sir

I thank you very sincerely for the articles on Viola tricolor and Asparagus, and particularly for your note on a Plusia frequenting Viola tricolor and on a moth visiting Glyceria fluitans.1

Can a grass secrete nectar? Reading Conr. Sprengels wonderful work, who p. 80 affirms, that in the flowers of Secale cereale nectar is secreted by the lower part of the ovarium, I have myself, already some years ago, started this question.2 But overcharged by other observations I have neglected to examine the pretended nectar secretion of Gramineae, and at last I have forgotten this subject. This-day I was surprised by your question and certainely I will prosecute it farther. Today, the flowers of our other grasses being not yet developped I examined only the flowers of Poa annua.3 I could not find drops of nectar secreted; but the two petala of the flower are swollen and very succulent; they have quite the appearance of nectaria. Even if they never secrete drops of nectar (this happens possibly in sunny weather), a moth will certainly be able to suck the liquor enclosed in the succulent petala. Farther searchings will decide it.

Newly I have repeatedly seen bees sucking the flowers of Viola tricolor; but undoubtedly also Lepidoptera are able to reach its nectar. The opinion of Mr Bennet, that this flowers are exclusively or almost exclusively fertilised by species of Thrips is certainly erroneous, likewise his assertion that the flowers of Viola tricolor are adapted to cross-fertilisation by dichogamie.4

According to Mr. Thomas Meehans article the fertilisation of Asparagus would wholly be accomplished by the wind.5 Having repeatedly seen different species of bees frequenting the flowers of this plant and sucking the nectar as well of the femal as of the male flowers, I can scarcely believe that Mr. Meehans observation is correct. But afterwards I will expressly examine whether the pollen of Asp. is dry and able to be disseminated by the wind.

With repeated thanks | yours sincerely | H. Müller.

[Enclosure]

diagram

The two petala are swollen and very succulent; they have the appearance of nectaria.

1
CD’s note has not been found. Müller had expressed his wish to see an article by Alfred William Bennett on Viola tricolor (Bennett 1873; see letter from Hermann Müller, 19 May 1873 and n. 4). Thomas Meehan had discussed the fertilisation of asparagus at a meeting of the Academy of Natural Sciences of Philadelphia (see Meehan 1872b). Plusia is a genus of moths. Glyceria fluitans is a species of aquatic perennial grasses; Mythimna pudorina (the striped wainscot moth) feeds on both its pollen and its nectar (Heath et al. 1979–, 9: 262; see also letter to Friedrich Hildebrand, 15 May 1873).
2
Christian Konrad Sprengel’s discussion of the secretion of nectar in Secale cereale (rye) is in Sprengel 1793, pp. 79–80. In his copy of Sprengel 1793, p. 79 (Darwin Library–CUL), CD noted that Sprengel confessed in his introduction that he knew ‘no use for nectar in grasses’ (see Marginalia 1: 780).
3
Poa annua is annual meadow-grass.
4
Müller refers to Bennett 1873 (see n. 1, above). Sprengel coined the term dichogamy to describe the condition in which male and female sex organs of a hermaphroditic flower mature at different times (Sprengel 1793, pp. 17–19).
5
See Meehan 1872b, p. 139.

Please cite as “DCP-LETT-8923,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-8923