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Darwin Correspondence Project

To Friedrich Hildebrand   15 May 1873

Down, | Beckenham, Kent.

May 15 1873

Dear Sir

I want to beg a favour of you— I could myself find some of the information which I require, in your several papers; but it wd take me much time to search for the facts, & perhaps I might not find all.

I remember that with Primula, & I think Corydalis, & perhaps in other cases, you fertilized some flowers with pollen from the same flower, & other flowers with pollen from distinct flowers borne by the same plant.1 I have neglected to make such observations, excepting once or twice, & I want much to know what difference there is in the number of the seeds in the two cases. Now will you be so kind as to tell me the result of all such experiments as you have made—

If you have the calculations ready, I shd like to hear the result, taking the number of seeds produced by flowers fertilized by other flowers on the same plant, as 100. I wish to quote all yr observations in full, or at least to give a few cases as illustrations.

Hoping that you will grant me this favour, I remain | My dear Sir | yours very faithfully | Ch. Darwin

P.S. I read with the greatest interest your paper on the distribution of the seeds of the Graminæ. I was particularly struck with your argument about the cultivated cereals.2 I may add, though it relates to rather a different point, that I have seen 2 accounts of moths frequently visiting the flowers of Glyceria fluitans, which makes me suppose that they must secrete nectar!3


In Variation 2: 132–3, CD had referred to Hildebrand’s experiments on fertilising Primula and Corydalis, whose flowers are dimorphic (Hildebrand 1864 and 1866b).
In Hildebrand 1872, pp. 740–1, Hildebrand pointed out that cultivated cereals, owing to their sensitivity to the weather, lost even more pollen than wild grasses, which lost two-thirds of their pollen to the wind. Early in the season, when conditions were wetter, there was more self-fertilisation by cultivated cereals; in warmer, dryer weather later in the season there was more cross-fertilisation.
Mythimna pudorina (the striped wainscot moth) feeds on both the pollen and the nectar of Glyceria fluitans, a species of aquatic perennial grass (Heath et al. 1979–, 9: 262). The two accounts have not been identified, but CD had noted in his 1861 abstract of Kurr 1833 that Poa aquatica, another grass, probably had nectar (see Marginalia 1: 472).


Hildebrand, Friedrich. 1864. Experimente über den Dimorphismus von Linum perenne und Primula sinensis. Botanische Zeitung 22: 1–5.

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.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Asks for results of FH’s experiments fertilizing some flowers with pollen from the same flower, & other flowers with pollen from distinct flowers borne by the same plant.

Has read FH’s paper on the distribution of the seeds of the Graminæ (Hildebrand 1872, pp. 740–1) with great interest.

Please cite as

Darwin Correspondence Project, “Letter no. 8912F,” accessed on 23 September 2020,

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