To Friedrich Hildebrand   20 April [1866]

Down. | Bromley. | Kent. S.E.

April 20th

Dear Sir

I am very much obliged to you for so kindly sending me your most interesting papers.1 The cases of Lopezia & Schizanthus are quite new to me.2 A Botanical friend, Mr. Henslow, was staying here a fortnight since, & detected & showed to me the curious movements in Indigofera, which grew in my greenhouse.—3

You may perhaps like to hear that in 1860 I watched Bombus lapidarius sucking the flowers of Pedicularis sylvatica, & I saw all that you describe: when the Bee forced its head into the corolla, the slit in the upper helmet-like petal opened & the anthers & stigma were rubbed on its back, so that its back was white with pollen.—4

Several years ago I protected Medicago lupulina from insects, & its fertility was much impaired, but not wholly prevented.5 I know of many cases in which in the same genus one species requires insect aid & another is sufficiently or fully fertile without such aid; but in this latter case the flowers are nevertheless repeatedly crossed by adjoining plants.

I have not yet read your paper on Salvia, but I recognize the beautiful structures in your excellent drawings with which I am familiar.—6

I hope that you will continue your interesting researches, & with sincere respect, | remain Dear Sir | Yours truly obliged | Ch. Darwin

Postmark: AP 20 66

1
CD had received copies of Hildebrand 1866a and 1866b. See letter to George Henslow, 16 April [1866] and nn. 2 and 5.
2
For Hildebrand’s descriptions of Lopezia coronata (a synonym of L. racemosa subsp. racemosa)and Schizanthus pinnatus, see Hildebrand 1866a, pp. 75–7.
3
George Henslow had visited CD from 2 to 3 or 4 April 1866 (Emma Darwin’s diary (DAR 242)). He had been preparing a paper on pollination mechanisms in Indigofera (see letter to George Henslow, 16 April [1866] and n. 2).
4
Pedicularis sylvatica, commonly known as lousewort, is described in Hildebrand 1866a, pp. 10–11. CD reported his observations of bees visiting P. sylvatica in Cross and self fertilisation, p. 422.
5
CD had written a note on Medicago lupulina that was included in a paper by Henslow on cross-pollination by insects in Medicago sativa (Henslow 1865). See Correspondence vol. 13, letter to George Henslow, [2–5 November 1865]. CD’s observations were also published in Cross and self fertilisation, p. 368. His notes on M. lupulina, dated 1859, are in DAR 157a: 45.
6
CD refers to Hildebrand 1866b. See letter to George Henslow, 16 April [1866] and n. 5.

Manuscript Alterations and Comments

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Please cite as “DCP-LETT-5062A,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-5062A