The letter was published in the Gardeners’ Chronicle on 10 February 1866 under the heading ‘Partial change of sex in unisexual flowers’. See also Collected papers 2: 130–1. Apparently, the editors’ note was the only reply to this letter (see n. 2, below).

CD refers to plants with unisexual male and female flowers that are borne separately, on the same (monoecious) plant or on distinct (dioecious) plants. Under the printed letter, the editors noted their observation of willow flowers with one stamen and a stalked carpel, and cited instances of anthers developing from an ovary in members of the Euphorbiaceae. The sole reference to the variable development of the male and female parts of unisexual flowers in Variation is the mention of John Scott’s observations in maize (Variation 1: 321; see also Correspondence vol. 12, letter from John Scott, 12 [February 1864] and n. 8, and Scott 1863). For examples of CD’s early interest in transitional states between hermaphroditism and unisexuality in plants and animals, see Notebooks, Notebook C, 167; Notebook D, 157–9. CD later devoted a chapter to the subject in Forms of flowers (pp. 278–309).

Gynandromorphy, that is, the occurrence of male and female characters in the same individual, is illustrated by a beetle and some moths in Westwood 1831, of which there is a copy in the Darwin Library–CUL. Westwood 1831 contains references to further papers on gynandromorphy in insects from the first volume of the Zoological Journal and the fifteenth volume of the Transactions of the Linnean Society of London, both of which CD had read earlier (see ‘CD’s reading notebooks’, Correspondence vol. 4, Appendix IV). CD alluded to half-male and half-female insects in earlier discussions of the possibility that flowers are fundamentally bilateral (see Correspondence vol. 4, letter to J. D. Hooker, [2 June 1847] and n. 4). In Variation 2: 400, he considered insects in which exactly one half or one quarter of the body resembled the male, and the other half or three quarters the female, as examples of the latency of characters.