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Darwin Correspondence Project

To W. T. Thiselton-Dyer   2 August [1878]1

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

August 2d

My dear Dyer

I thank you for a heap of things. The Arachis arrived in admirable condition, & I have been observing it ever since. I have no doubt the pointed gynophores cd. penetrate the ground without any aid; but they seem to be always in movement: I cd not resist dissecting one & what a curious structure it is!2 I also received a fine Pinus which has likewise been under observation: I have written to Messrs Barron to know what I am indebted to them.3 Pray thank Mr Smith for trouble he has kindly taken about the Pinus.—4

I had forgotten about Tropæolum & will raise some plants. Many thanks for Oxalis seeds; they are treasures to me.—5

Please tell Sir Joseph that I am particularly obliged for name of Trifolium, which by accident was sent me from Kew as T. resupinatum: it has removed a load off my mind, for I thought I must have been mad last year, the two Trifoliums behaved so differently.— If at end of month or later in autumn I could any how get seeds of true T. resupinatum, they wd be of great value to us, for Sachs has been suggesting a notion about bloom to Frank, which the leaves of T. resupinatum & of no other plant in world would perhaps solve.—6 This is my sole request at present.

Yours very truly | Ch. Darwin

I remember the roots, which you showed me at Kew, but forget whether they were positively or negatively heliotropic & what kind of plant it was.—7


The year is established by the relationship between this letter and the letter from J. D. Hooker, 31 July 1878.
CD had asked Thiselton-Dyer for a new plant of Arachis hypogaea (peanut) in order to observe the action of the gynophore, an elongated tube developed from the ovary after fertilisation (see letter to W. T. Thiselton-Dyer, 19 July [1878]).
The firm of William Barron & Son had nurseries at Borrowash, Derbyshire; conifers were a specialty of theirs (Elliott et al. 2007, p. 137). CD’s letter to the firm has not been found. CD had asked Thiselton-Dyer for a larger specimen of a fir tree, noting that he had made observations on a small plant of Pinus pinaster (maritime pine; see letter to W. T. Thiselton-Dyer, 19 July [1878] and n. 6).
John Smith was the curator of the Royal Botanic Gardens, Kew.
Tropaeolum is the genus of nasturtiums. CD had described the sleep of Oxalis valdiviana (a synonym of O. valdiviensis, Chilean yellow-sorrel), O. rosea (pink sorrel), and O. floribunda (abundant flowering wood sorrel) in his letter to Thiselton-Dyer of 18 June [1878] and asked for seeds of other species of Oxalis.
Joseph Dalton Hooker had identified the plant as Trifolium striatum (knotted clover; letter from J. D. Hooker, 31 July 1878). Trifolium resupinatum is Persian clover. Julius Sachs had suggested that one function of bloom was to protect the leaf stomata (breathing pores) from water (see letter from Francis Darwin, 24 and 25 July 1878; see also F. Darwin 1886, p. 99). In observations made the previous summer, CD had noted that half the lateral leaflets had no bloom on their abaxial (lower) surface (see Correspondence vol. 25, letter to W. T. Thiselton-Dyer, [20–4 August 1877] and n. 4).
See letter from W. T. Thiselton-Dyer, 11 May 1878 and n. 5. CD had visited Kew on 22 January 1878 (letter to Asa Gray, 21 [and 22] January 1878). CD had been shown the positively heliotropic aerial roots of an orchid collected in the Admiralty Islands.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Darwin, Francis. 1886. On the relation between the ‘bloom’ on leaves and the distribution of the stomata. [Read 4 February 1886.] Journal of the Linnean Society (Botany) 22 (1885–6): 99–116.


Thanks for plants and seeds; requests for more to test Sachs’s notion on "bloom".

Please cite as

Darwin Correspondence Project, “Letter no. 11637,” accessed on 17 April 2021,