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Darwin Correspondence Project

To Francis Darwin   10 October 1873

Down, | Beckenham, Kent.

Oct 10. 1873

You had better take this note to Kew and read to Hooker.1

My dear Frank

When you next come home I want several answers about my microscope. Is ours “Nouveau petit modèle”?2 Mine is splendid.—

What are the numbers of your eye pieces & micrometer & object-glasses? Copy them down.—

Are the object glasses “à grande ouverture”?3

Take great care of enclosed papers.4

You must not bother Klein,5 but perhaps you can find out from him the value of the micrometer measures in the enclosed tableau: (what are they decimal places of?) some of the figures are written so badly that I can’t read them. Hartnack owes me 73f—& I think I can’t do better, for yr sake if not for my own, than order an immersion lens, & you must learn how to use it.6

You must find out from Klein whether we had better order Nos. 9, 10 or 11 &c at p. 3 of enclosed.

Now tell Hooker that the price is under £15. Hartnack in his recent circular does not allude to a London agent, & I shd think it wd be safer to order from Paris.7 After Oct 15 his address will be

“Rue Bonaparte No 1.”


Tell Hooker I am working hard at Desmodium & that I have found out what I believe are new movements—8 It wd be an immense aid to me if he cd lend or give me any other sp. of Desmodium whether or not it appears to move with the 2 lateral leaflets not almost rudimentary as in D. gyrans; especially if the leaves look silvery when dipped in water i.e. are protected by coating of wax.

Ask H. whether he has a plant of Drosophyllum alive—9 If so I wd ask him to try an exp. w. wd not take more than 5m.

When in Kew gardens see if there is any Helianthemum or Cistus in flower— if so try whether stamens are irritable when touched with fine hard object; if they are flick water hard into the flower & see if they act—

yours affect— | Ch. Darwin

I think my plant of Desmodium will last out, but if I kill it can H. give me another. It suffers a terrible amount of syringing.10


Joseph Dalton Hooker was director of the Royal Botanic Gardens, Kew (ODNB). This letter was previously published in Correspondence vol. 21 from a copy in DAR 153: 21.
CD had purchased a microscope from the German maker, Edmund Hartnack, in June 1873 (see Correspondence vol. 21, letter from Francis Darwin, [before 26 June 1873]). Nouveau petite modèle: new small model (French).
À grande ouverture: large aperture. CD later wrote that he used a no. 8 object-glass of Hartnack to examine the small bladders of Utricularia neglecta (Insectivorous plants, p. 411).
The enclosure has not been found. It was probably a price list from Hartnack.
Edward Emanuel Klein had advised Francis on the purchase of a microscope (see Correspondence vol. 21, letter from Francis Darwin, [before 26 June 1873]).
Immersion lenses were designed to view objects through a liquid medium, reducing the loss of light and yielding greater penetration (see Carpenter 1875, pp. 46–7).
Hooker was evidently considering the purchase of a Hartnack microscope; CD had ordered his from Paris (see Correspondence vol. 21, letter from Francis Darwin, [before 26 June 1873]). In his Classed account books (Down House MS), CD recorded a payment of £16 8s. for ‘Hartnack &c’ on 26 June 1873.
CD discussed the movements of Desmodium gyrans (the telegraph or semaphore plant) in Movement in plants, pp. 357–65. Desmodium gyrans is a synonym of Codariocalyx motorius.
Drosophyllum is a monospecific genus. CD had acquired specimens of the only species, Drosophyllum lusitanicum (the Portuguese sundew or dewy pine), in 1869 (see Correspondence vol. 17, and Insectivorous plants, p. 332).
CD mentioned syringing Desmodium gyrans in Movement in plants, p. 363. He had received specimens from Kew in October 1862 and July 1877, but there is no record of one sent in 1873 (Royal Botanic Gardens, Kew, Outwards book).


Carpenter, William Benjamin. 1875. The microscope and its revelations. 5th edition. London: J. and A. Churchill.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Insectivorous plants. By Charles Darwin. London: John Murray. 1875.

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

ODNB: Oxford dictionary of national biography: from the earliest times to the year 2000. (Revised edition.) Edited by H. C. G. Matthew and Brian Harrison. 60 vols. and index. Oxford: Oxford University Press. 2004.


Asks for details about microscope parts.

Wants FD to ask Hooker for species of Desmodium; CD believes he has found new movements.

Also ask whether Hooker has Drosophyllum.

Letter details

Letter no.
Charles Robert Darwin
Francis Darwin
Sent from
Source of text
Royal Botanic Gardens, Kew (JDH/3/6 Insectivorous plants 1873-8 f.1)
Physical description
LS(A) 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 9095,” accessed on 4 June 2023,

Also published in The Correspondence of Charles Darwin, vol. 21 and 24 (Supplement)