To W. T. Thiselton-Dyer   11 October [1877]1

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

Oct 11

My dear Dyer

The fine lot of seeds arrived yesterday & are all sown & will be most useful.2 If you remember pray thank Mr Lynch for his aid.3 I had not thought of Beech or Sycamore, but they are now sown.—

Perhaps you may like to see rough copy of tracing of movements of one of Cotyledons of Red Cabbage, & you can throw it into fire.4 A line joining the 2 Cots. stood facing N.E window, & the day was uniformly cloudy. Bristle was gummed to 1 Cot. & beyond it a triangular bit of card was fixed & in front a vertical glass. A dot was made in glass every $\frac{1}{4}$ or $\frac{1}{2}$ hour at point where end of bristle & apex of card coincided, & the dots were joined by straight lines. The observation was from 10o A.M & 8o 45 P.M. During this time the enclosed figure was described; but between 4o P.M. & 5o 38 P.M the Cot. moved so that the prolonged line was beyond the limits of the glass & the course is here shown by imaginary dotted line.—

The Cot. of Primula Sinensis moves in closely analogous manner, as do those of a Cassia.5 Hence I expect to find such movements very general with cotyledons & I am inclined to look at them as the foundation for all the other adaptive movements of leaves. They certainly are of the so-called sleep of plants.6 I hope I have not bothered you— Do not answer.—

I am all on fire at the work.— I have just had a short & very prosperous note from Asa Gray, who says Hooker is very prosperous & both are tremendously hard at work.—7

Yours very sincerely | Ch. Darwin

[DIAG HERE]

Footnotes

The year is established by the reference to Asa Gray’s letter (see n. 7, below).
CD had asked for seeds of three or four plants that produced large cotyledons (see letter to W. T. Thiselton-Dyer, 7 October 1877).
Richard Irwin Lynch was foreman of the propagating department at the Royal Botanic Gardens, Kew. In August, he began helping CD to investigate plant movement (see letter to R. I. Lynch, 23 August [1877], and letter from R. I. Lynch, [28 August 1877]).
The diagram is reproduced at 75 per cent of its original size. CD later described this case in Movement in plants, pp. 15–16.
CD described the movements of the cotyledons of Primula sinensis (Chinese primrose) and of the legume Cassia tora in Movement in plants, pp. 45–6 and 34–5.
The leaves of sleeping plants gradually assume a vertical position so as to protect their upper surfaces from cold (Movement in plants, p. 3).
Asa Gray and Joseph Dalton Hooker were busy organising their collections before Hooker’s departure for England, as they intended to prepare a survey of the vegetation of the Rocky Mountains (J. D. Hooker and Gray 1880); they had botanised together in the region over the summer (see letter from Asa Gray, 27 September 1877).

Bibliography

Movement in plants: The power of movement in plants. By Charles Darwin. Assisted by Francis Darwin. London: John Murray. 1880.

Summary

Movements in cotyledons; outlines tracing technique. [A tracing of movements of red cabbage cotyledon enclosed.]