The date is established by the relationship between this letter and the letter from W. E. Darwin, [19 May 1864], and by George Howard, Francis, and Leonard Darwin’s arrival at Down on 21 May 1864 (see n. 5, below).

In his letter of [19 May 1864], William mentioned sending drawings of pollen and anthers, as well as a tin case enclosing both flower forms of the dimorphic Menyanthes trifoliata.

CD’s Menyanthes seeds, acquired from Joseph Dalton Hooker, had failed to germinate (see Correspondence vol. 10, letter to J. D. Hooker, 9 [April 1862] and n. 3, note in DAR 110: B52, and Forms of flowers, p. 115).

See letter from W. E. Darwin, [19 May 1864] and n. 8. The photographs arrived later (see, for example, letter to Asa Gray, 28 May [1864]).

See letter from H. E. Darwin to W. E. Darwin, [18 May 1864] and n. 4.

See letter from W. E. Darwin, [19 May 1864] and n. 3.

CD wrote in Forms of flowers, p. 115, that the short-styled Menyanthes trifoliata appeared to be sterile with its own pollen. However, in this letter, CD may be referring to recently acquired information on the self-pollination of Menyanthes flowers that were submerged and closed (see note in DAR 111: A69 and Forms of flowers, pp. 311–12). The note in DAR 111: A69 on self-pollinated Menyanthes flowers mentions a comment of Sarah Elizabeth Wedgwood’s on seeing Menyanthes at Maer, Staffordshire; Sarah Elizabeth Wedgwood, who lived at Maer until 1847, had recently visited Down (see letter from Emma Darwin to W. E. Darwin, [17 May 1864] and n. 4). For CD’s speculation on the self-fertility of short-styled Pulmonaria angustifolia, see letter to W. E. Darwin, 14 May [1864] and nn. 6 and 7.