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Darwin Correspondence Project

To George Henslow   [2–5 November 1865]1

[Note on Medicago lupulina, communicated by Mr. Darwin:—]

“I covered a number of plants with a net (which I know does not injure their seeding), and left others close by uncovered, and these were visited incessantly by bees. I could not compare their relative fertility with accuracy, on account of the easy shedding of the seed; but I gathered 150 not quite ripe pods of both; those from under the net weighed 77 grains, and those visited by the bees weighed 101 grains. No doubt the difference in the weight of the seed would have been considerably greater, as the pod is formed independently of the number of seeds.”2


The date range is established by the relationship between this letter and the letters from George Henslow, 1 November 1865 and 6 November 1865.
CD reported these observations of Medicago lupulina in response to a request from Henslow, who had noted an ‘irritability in the stamens’ of M. sativa that seemed to facilitate cross-pollination by insects (see letter from George Henslow, 1 November 1865 and nn. 5–9, and G. Henslow 1865). CD’s observations were also published in Cross and self fertilisation, p. 368. CD’s notes on M. lupulina, dated 1859, are in DAR 157a: 45.


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

Henslow, George. 1865. Note on the structure of Medicago sativa, as apparently affording facilities for the intercrossing of distinct flowers. [Read 16 November 1865.] Journal of the Linnean Society (Botany) 9 (1867): 327–9.


Reports the results of an experiment to compare the weight of seeds produced in plants of [Medicago sativa] by self-pollination and by insect pollination.

Letter details

Letter no.
Charles Robert Darwin
George Henslow
Sent from
Source of text
Journal of the Linnean Society (Botany) 9 (1867): 328 n.

Please cite as

Darwin Correspondence Project, “Letter no. 4929F,” accessed on 30 May 2023,

Also published in The Correspondence of Charles Darwin, vol. 13