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Darwin Correspondence Project

To J. D. Hooker   14 May [1860]

Down Bromley Kent

May 14th

My dear Hooker

I daresay you will be too busy to give instructions about the fertilisation of Leschenaultia;1 but in case you do, I write to say that I find the way to do it, is to move a camel-pencil, holding handle nearly parallel to the pistil & axis of flower, just in same direction & manner as the belly of a Bee would brush over the indusium, whilst crawling in to suck the copious nectar; & then the points of the brush hit against the rough protuberant lip, open the indusium, & some of the hairs enter & stir up the pollen splendidly & generally bring out some grains. So that the operation is done in a second, & I feel nearly sure that every bee which sucks this flower will open the indusium, stir up the pollen, remove some, & often leave pollen from other flowers within the indusium.

In fact I am at ease about Leschenaultia; but shd like excessively to prove that stirring up the pollen within the indusium is necessary or favourable to fertilisation. For then I shd look at this curious contrivance, as specially related to visits of insects; as I begin to think is almost universally the case. The evidence about dioicous condition of Cowslips & Auriculas seems to me to get clearer & clearer.—

And now I will (honour bright) not bother you with another note for a long time—that is if I can possibly resist

Yours affecty | C. Darwin

Poor dear Etty is a little better; not seriously ill, but our Doctor, who comes daily, says the Fever may run on for a considerable time. She eats hardly anything, but does not weaken so rapidly as I shd. have feared.2

P.S. | Very hearty thanks for your pleasant note (& Mrs. Hooker’s) just received. I daresay after all my vows I shall not resist answering it.—

I find before flowers are utterly withered of Cowslips the seeds of “females” are twice as big as seeds or ovules in the “Male” flowers—   Hence I expect the latter will abort entirely. Out of 522 flower stalks gathered by the children I find 281 males & 241 Females.—3


Henrietta Emma Darwin had been diagnosed as suffering from a form of typhus fever. See letter to J. D. Hooker, 11 May [1860].
These observations are recorded in CD’s Experimental book, pp. 55 and 56 (DAR 157a). CD’s paper ‘On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations’ discusses these points (Collected papers 2: 45–63). See also preceding letter and n. 5.


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


Instructs JDH on how to pollinate Leschenaultia.

Evidence of Leschenaultia and the dioecious condition of cowslips and Auricula is making necessity of insect pollination "clear and clearer".

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 115: 55
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 2800,” accessed on 17 September 2023,

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