To W. T. Thiselton-Dyer   15 September [1877]1

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

Sept. 15th

My dear Dyer

In my note yesterday to Mr. Lynch I asked him to observe whether Euphorbia jacquiniæflora moved when shaken; & if it did so, to ask you whether the plant cd. be spared & sent us.2 But on further consideration with Frank, I think the movements of the leaves ought to be traced on the revolving frame for the 24 hours, for so few plants without “cushions” at the bases of the petioles have been observed.3 I know only of Pfeffers observations on Nicotiana rustica. I presume there are no such “cushions” or “glands” or whatever they ought to be called with the Euphorbia.—4

Ever yours | C. Darwin

1
The year is established by the relationship between this letter and the letter to R. I. Lynch, 14 September 1877.
2
See letter to R. I. Lynch, 14 September 1877 and n. 4. Richard Irwin Lynch was foreman of the propagation department at the Royal Botanic Gardens, Kew.
3
Francis Darwin was assisting CD with experiments on movement in plants. CD referred to ‘a so-called joint, cushion or pulvinus’ as an aggregate of small cells that had ceased to increase in size from a very early age (Movement in plants, p. 2). For CD’s conclusions on the role of the pulvinus in movement in cotyledons and in nyctitropic movements in leaves, see Movement in plants, pp. 112–13 and 396–7.
4
Wilhelm Pfeffer had discussed movement in Nicotiana rustica (Aztec or wild tobacco) in Pfeffer 1875, pp. 17–18, 29, 51, and 175, concluding that it was caused by alternate swelling of the cells of the pulvinus, without the cells themselves exhibiting any further growth (see also Movement in plants, p. 2). CD observed that the sinking movement in young leaves of Euphorbia jacquiniiflora was due to the downward curvature of the petiole, ‘no part of which exhibited any structure like that of a pulvinus’ (Movement in plants, p. 388), and concluded that the nature of the movement was similar whether a pulvinus was absent or present (ibid., p. 396).

Manuscript Alterations and Comments

1.1 my] after del illeg
1.3 & sent us.] interl
1.7 the] interl

Please cite as “DCP-LETT-11141,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11141