The conjectured date is based on Emma Darwin’s diary, in which she recorded that CD went to London on Tuesday, 20 March 1855, and returned on Saturday the 24th. Some notes by CD dated 25 March 1855 (DAR 205.4: 68) begin with ‘M^r Bunbury says …’ and suggest that CD had recently met Bunbury.

CD wished to discuss the flora of Madeira and the Cape of Good Hope with Bunbury, who had travelled in both areas (F. J. Bunbury ed. 1891–3, Early life: 247 and Middle life 2: 158; see also letter to Charles Lyell, 18 February [1854], n. 1). In the notes of his conversation with Bunbury (see n. 1, above), CD commented on the presence of northern genera on Madeira and the absence of any northern species, the absence of northern plants on Table Mountain, South Africa, and the distribution of the fern Pteris longifolia (longleaf brake) in Ischia, Tenerife, and Sicily. CD had not attended the meeting of the Linnean Society (6 March 1855) at which Bunbury had read the first section of his paper that dealt with the flora of Madeira (C. J. F. Bunbury 1857). The paper had, however, been summarised in Gardeners’ Chronicle and Agricultural Gazette, no. 11, 17 March 1855, p. 175. See also letter from J. D. Hooker, [before 17 March 1855], in which it appears that Hooker had some criticisms of Bunbury’s paper.