The date range is conjectured by the relationship between this letter and the letter from W. E. Darwin, [28 June 1863?] (Correspondence vol. 24, Supplement).

See Correspondence vol. 24, Supplement, letter from W. E. Darwin, [28 June 1863?].

CD made a series of observations on Oxalis, beginning in April 1862 and ending in 1869; his experimental notes on this genus are in DAR 109: B3–27, B101, B108, and DAR 111: A44–48, B33–5, B43. CD’s experiments on species of Oxalis native to Britain focused chiefly on O. acetosella, and were concentrated in the spring and summer of 1863 and 1864 (DAR 109: B3–7 and DAR 111: A44, A46–8). CD’s interest in the occurrence of dimorphism in species of Oxalis began in 1861 (see Correspondence vol. 9, letters to George Bentham, 24 November [1861] and 30 November [1861]). He pursued investigations on heterostyly (see, for example, Correspondence vol. 10, letters to Daniel Oliver, 20 [April 1862], 24 April [1862], and this volume, letter to Roland Trimen, 23 May [1863]), and on cleistogamy (see, for example, letter to Journal of Horticulture and Cottage Gardener, [17–24 March 1863] and n. 7, and letter to Asa Gray, 31 May [1863]). CD published the results of his observations in Forms of flowers, pp. 169–183, 321–4.