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Darwin Correspondence Project

To Fritz Müller   14 May 1877

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

May 14. 1877

My dear Sir,

I wrote to you a few days ago to thank you about Pontederia,1 & now I am going to ask you to add one more to the many kindnesses which you have done for me. I have made many observations on the waxy secretion on leaves which throw off water (e.g. cabbage, tropæolum) & I am now going to continue my observations.2 Does any sensitive species of mimosa grow in your neighbourhood? If so will you observe whether the leafletes keep shut during long-continued warm rain. I find that the leaflets open if they are continuously syringed with water at a temperature of about 19c but if the water is at a temperature of 33–35c they keep shut for more than 2 hrs & probably longer. If the plant is continuously shaken so as to imitate wind the leaflets soon open. How is this with the native plants during a windy day? I find that some other plants, for instance Desmodium3 & Cassia, when syringed with water, place their leaves so that the drops fall quickly off; the position assumed differing somewhat from that in so called sleep. Would you be so kind as to observe whether any of your plants place their leaves during rain so as to shoot off the water; & if there are any such I should be very glad of a leaf or two to ascertain whether they are coated with a waxy secretion

There is another & very different subject, about which I intend to write & should be very glad of a little information. Are earth worms (Lumbricus) common in S. Brazil, & do they throw up on the surface of the ground numerous castings or vermicular masses such as we so commonly see in Europe? Are such castings found in the forests beneath the dead & withered leaves. I am sure I can trust to you kindness to forgive me for asking you so many questions4

my dear Sir | Yours sincerely | Charles Darwin


CD had begun studying bloom (the epicuticular waxy coating on the leaves and fruit of many plants) in August 1873 (see Correspondence vol. 21, letter to J. D. Hooker, 13 August 1873 and n. 2). He carried out experiments to compare the effects of water on berries and leaves with the bloom left on and on those that had the bloom removed (see DAR 66: 8, 24). He suspended his work on the subject in 1874 in order to concentrate on finishing Insectivorous plants (see Correspondence vol. 22, letter to W. T. Thiselton-Dyer, 28 [June 1874] and n. 7). CD never published on bloom, but Francis Darwin published some of the results of their experiments, made in 1878, in his paper ‘On the relation between the “bloom” on leaves and the distribution of the stomata’ (F. Darwin 1886).
The genus Desmodium is commonly known as tick clover.
CD had worked intermittently on the action of earthworms (Lumbricus terrestris) since the late 1830s, when he published ‘Formation of mould’. He had given the subject more systematic attention in 1871 and 1872; see Correspondence vols. 19 and 20.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 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.

‘Formation of mould’: On the formation of mould. [Read 1 November 1837.] Transactions of the Geological Society of London 2d ser. 5 (1840): 505–9. [Shorter publications, pp. 124–7.]

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


Requests observations on sensitive Mimosa and movements of plants in rain.


Letter details

Letter no.
Charles Robert Darwin
Johann Friedrich Theodor (Fritz) Müller
Sent from
Source of text
The British Library (Loan MS 10 no 42)
Physical description
LS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 10960,” accessed on 21 June 2024,