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Darwin Correspondence Project

To J. D. Hooker   7 May [1860]1

Down Bromley Kent

May 7th. —

My dear Hooker

Do you chance to know any observing man living in the country (whatever country that may be) inhabited by the Leschenaultia formosa?2 I am very unhappy about this flower; & I can “wriggle out” of my difficulty only by supposing that Bees go from flower to flower & open the indusium. I know that Bees will do more difficult work for pollen. Our English Bees will not look at the flower. I would write & supplicate anyone (& use your name as Introduction), if any naturalist lives in country of Leschenaultia, to watch the Bees at work.—3

I have this morning been looking at my experimental Cowslips & I find some plants have all flowers with long stamens & short pistils which I will call “male plants”—others with short stamens & long pistils, which I will call “female plants”.4 This I have somewhere seen noticed, I think by Henslow;5 but I find (after looking at only two sets of plants) that the stigma of male & female is of slightly different shape & certainly different degree of roughness, & what has astonished me the pollen of the so-called female plant, though very abundant, is more transparent & each granule is exactly only 23 of size of pollen of the so-called male plant.—   Has this been observed?? I cannot help suspecting that the cowslip is in fact dioicous—but it may turn out all blunder, but anyhow I will mark with sticks the so-called male & female plants & watch their seeding. It would be fine case of gradation between an hermaphrodite & unisexual condition.—   Likewise a sort of case of Balancement of long & short pistils & stamens.—   Likewise perhaps throws light on Oxlips.—6

Yours affect. | C. Darwin

You will be sorry to hear that poor Etty has a remittent Fever, it is now become slight, but will run out for 14 or 21 days, the Doctor tells us.—   It reduces her & exhausts her much.—7

I have now examined Primroses & find exactly same difference in size of pollen, correlated with same difference in length of style & roughness of stigma!—

*uCowslips & Primroses*u Male plants. long stamens, big pollen-grains, short style, smooth stigma, Female plants short stamens, small 〃 〃, long 〃, rough 〃,

I measured pollen-grains in water & dry by Micrometer.—


The endorsement is confirmed by the relationship to the letter from J. D. Hooker, [28 April 1860].
Leschenaultia formosa is a native of Australia. Hooker had supplied specimens of this species for CD’s investigation of the plant’s pollination mechanism (see letters to J. D. Hooker, [26 February or 4 March 1860] and 12 March [1860]). CD’s experiments are recorded in his Experimental book, pp. 50–2 (DAR 157a).
See letters to J. D. Hooker, 15 [May 1860], and to James Drummond, 16 May 1860.
CD’s observations on cowslips, dated 8 May 1860, are recorded in his Experimental book, p. 53. His work and the identification of two kinds of cowslip flower were eventually described in a paper ‘On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations’, published in the Journal of the Proceedings of the Linnean Society (Botany) 6 (1862): 77–96 (Collected papers 2: 45–63).
Henslow 1830. CD cited John Stevens Henslow’s work on primroses and cowslips in his ‘big book’ on species (Natural selection, pp. 129–30).
Oxlips were commonly thought to be the hybrid offspring of primroses and cowslips. CD, however, believed the oxlip to be a form intermediate between the two that retained characters of the common ancestor of cowslips and primroses (see Natural selection, pp. 132–3). See also letter from Henry Doubleday, 3 May 1860.
Henrietta Emma Darwin was seriously ill throughout much of 1860. Emma Darwin’s diary records the onset of her ill health on 28 April.


Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.


To understand Leschenaultia pollination CD requires field observations in the native country.

Has observed two forms of cowslips, which he calls male and female. The same two forms are found in primroses.

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 115: 52
Physical description
ALS 5pp

Please cite as

Darwin Correspondence Project, “Letter no. 2785,” accessed on 14 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 8