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Darwin Correspondence Project

From J. D. Hooker   15 January 1868

Royal Gardens Kew

Jany 15/68

Dear Darwin

W. R. Greg sent me a copy of a pamphet of which I asked for a copy for you, conceiving you to be the only man capable of throwing any light on the subject. I herewith send it— —& I only hope that you may be able to afford the poor Devil a ray of light, on what appears to me as obscure a problem as man has ever conceived.—1

Certainly many small flowered Cucurbitaceae, have smaller ♀ than ♀ fl.2 moreover ♀ are hidden in axils. ♂ in patent racemes.3

I wrote to Watson but have no answer, pointing out the counterbalance of crossing & also of uniformity of conditions which kill off all that are not reasonably like the parent. Watsons letter was like one who has forgotten the argument—4 I sent F Mueller the name of the Solanum like Acanth.5 All or most orders with opposite leaves present genera with that curious character, & it is a very curious one & always abnormal in the order eg Rubiaceæ, Melastomaceæ.

I do not understand Hildebrands Potatoes6   you must explain when I see you

Ever yr aff | J D Hooker

CD annotations

1.1 W. R. Greg … conceived.— 1.4] crossed pencil
2.1 Certainly … racemes. 2.2] enclosed in square brackets pencil; ‘Correlation, see Girou in 8vo. Pamph. 235 & Lucas Hered. Tom 2. 130 with References.’7 added ink; ‘Hooker has figures for Balanophoræ in his Paper Linn Transacts.’8 added pencil ‘Hooker one case of Parasitic plants, which grow on distinct species’ added ink
3.1 I wrote … argument— 3.3] crossed pencil
3.4 All … Melastomaceæ. 3.6] scored pencil; ‘Laws of Variation’ added pencil
3.5 & it is a very curious one] ‘ie opposite leaf very small’9 added pencil
4.1 I do not … see you] crossed pencil


Hooker refers to the pamphlet by William Rathbone Greg, Malthus: re-examined in the light of physiology ([Greg] 1868). CD’s annotated copy is in the Darwin Pamphlet Collection–CUL. The pamphlet was printed with blank pages interleaved, and carried a prefatory note requesting that readers ‘be kind enough to note down … any facts, or references … or qualifying considerations, which may occur to them … and then return the pamphlet thus enriched’.
Hooker meant ‘smaller female than male’.
No letter from CD to Hooker on this subject has been found; see however n. 7, below, and letter from J. D. Hooker [before 6 January 1868?].
Hooker refers to Hewett Cottrell Watson. See letter from H. C. Watson to J. D. Hooker, 1 January 186[8] and n. 7, and letter to J. D. Hooker, 6 January [1868].
Hooker refers to Fritz Müller. See letter to J. D. Hooker, 6 January [1868] and n. 8. The species was identified by Hooker as Gesneria pendulina (see letter to Fritz Müller, 30 January [1868]; see also n. 9, below).
The reference is to Friedrich Hildebrand’s graft hybridisation experiments with potatoes. See letter to J. D. Hooker, 6 January [1868] and n. 10.
The references are to Girou de Buzareingues 1831, an annotated copy of which is in the Darwin Pamphlet Collection–CUL, and to Prosper Lucas 1847–50, an annotated copy of which is in the Darwin Library–CUL (see Marginalia 1: 513–23). CD scored or annotated passages in each work that described structural differences between male and female flowers. In a sheet of notes in the back of his copy of the second volume of Lucas 1847–50, CD wrote a note on vol. 2, page 129: ‘Differences in Monoicous & Dioicous flowers … Sexual selection (Probably much correlation of growth’ (see Marginalia 1: 517).
The reference is to J. D. Hooker 1855. See letter from J. D. Hooker, [before 6 January 1868?].
In members of the Gesneriaceae, the family to which Gesneria belongs (see n. 5, above), and in the Solanaceae, opposite leaves are sometimes of different sizes (Hutchinson 1973, Willis 1973).


Girou de Buzareingues, Charles. 1831. Mémoire sur les rapports des sexes dans le règne végétal. Annals des Sciences Naturelles 24: 156–76.

Hutchinson, John. 1973. The families of flowering plants: arranged according to a new system based on their probable phylogeny. 3d edition. Oxford: Clarendon Press.

Lucas, Prosper. 1847–50. Traité philosophique et physiologique de l’hérédité naturelle dans les états de santé et de maladie du système nerveux: avec l’application méthodique des lois de la procréation au traitement général des affections dont elle est le principe. 2 vols. Paris: J. B. Baillière.

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.

Willis, John Christopher. 1973. A dictionary of the flowering plants and ferns. 8th edition. Revised by H. K. Airy Shaw. Cambridge: Cambridge University Press.


Sends a pamphlet by W. R. Greg [Malthus: re-examined by the light of physiology (1868)].

Many Cucurbitaceae have smaller male than female flowers.

Has written to H. C. Watson on the counterbalance [to variation] of crossing and uniform conditions. Watson has forgotten the argument.

Has written to F. Müller on abnormal Solanum.

Does not understand Hildebrand on potatoes.

Letter details

Letter no.
Joseph Dalton Hooker
Charles Robert Darwin
Sent from
Source of text
DAR 47: 193, 195
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 5787,” accessed on 20 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 16