To Fritz Müller   12 April 1881

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

April 12th. 1881

My dear Sir

I have delayed answering your last letter of Feb. 25th, as I was just sending to the printers the M.S. of a very little book on the habits of earth-worms, of which I will of course send you a copy when published.—1 I have been very much interested by your new facts on paraheliotropism, as I think that they justify my giving a name to this kind of movement, about which I long doubted. I have this morning drawn up an account of your observations, which I will send in a few days to ‘Nature’.2 I have thought that you would not object to my giving precedence to paraheliotropism, which has been so little noticed.— I will send you a copy of ‘Nature’ when published.—3

I am glad that I was not in too great a hurry in publishing about Lagestrœmia   I have procured some plants of Melastomaceæ, but I fear that they will not flower for two years & I may be in my grave before I can repeat my trials. As far as I can imperfectly judge from my observations, the difference in colour of the anthers in this family depends on one set of anthers being partially aborted. I wrote to Kew to get plants with differently coloured anthers, but I learnt very little as describers of dried plants do not attend to such points. I have, however, sowed seeds of 2 kinds, suggested to me as probable.—4 I have, therefore, been extremely glad to receive the seeds of Heteranthera reniformis. As far as I can make out it is an aquatic plant; & whether I shall succeed in getting it to flower is doubtful.5 Will you be so kind as to send me a postcard, telling me in what kind of station it grows.—

In the course of next autumn or winter, I think that I shall put together my notes (if they seem worth publishing) on the use or meaning of “bloom”, or the waxy secretion which makes some leaves glaucous.—6 I think that I told you that my experiments had led me to suspect that the movement of the leaves of Mimosa, Desmodium & Cassia, when shaken & syringed, was to shoot off the drops of water.7 If you are caught in heavy rain, I shd. be very much obliged, if you would keep this notion in your mind, & look to the position of such leaves.—

You have such wonderful powers of observation that your opinion wd. be more valued by me than that of any other man.— I have among my notes one letter from you on the subject, but I forget its purport. I hope, also, that you may be led to follow up your very ingenious & novel view on the two-coloured anthers or pollen, & observe which kind is most gathered by bees.8

Believe me | Yours ever sincerely | Charles Darwin

1
CD probably refers to the letter from Fritz Müller, 28 February 1881; the letter is known only from a printed source (Möller ed. 1915–21, 2: 409), and most of the text is missing. Either CD or Alfred Möller may have made an error about the date. CD hoped that Earthworms would soon be in print (see letter to R. F. Cooke, 10 April 1881). It was published on 10 October 1881 (Freeman 1977).
2
See letter to Nature, 14 April [1881]; CD included information from Müller that was probably in the now missing part of the letter from Fritz Müller, 28 February 1881. For Müller’s earlier observations on paraheliotropism (a term coined by CD to describe the movement of leaves during the day to reduce intense illumination), see the letter from Fritz Müller, 9 January 1881 and n. 8.
3
CD’s letter was published in Nature, 28 April 1881, pp. 603–4.
4
CD had studied plants of Lagerstroemia indica (crape myrtle, a member of the family Lythraceae) in 1863, when he was working on dimorphism and trimorphism; he noted the two different kinds of anthers and pollen and speculated about differences in stylar length (notes in DAR 109: B116–17 and DAR 27.2: A17), but concluded that the evidence for heterostyly in the species was ‘curiously conflicting’ (Forms of flowers, p. 168). In his letter of 7 February 1881, Müller had suggested that one type of anther served to attract insects, while the other type ensured cross-fertilisation. In reply, CD had mentioned his earlier experiments on plants in the family Melastomaceae (a synonym of Melastomataceae), noted for possessing different types of pollen and anthers (see letter to Fritz Müller, 20 March 1881 and nn. 2, 3, and 6). CD received dried plants of Monochaetum ensiferum (a synonym of M. calcaratum) and Centradenia floribunda from Kew and made observations on them on 3 April 1881 (notes in DAR 205.8: 21, 43).
5
See letter from Fritz Müller, 7 February 1881 and n. 5. No record has been found of Müller having sent seeds of Heteranthera reniformis (kidneyleaf mudplantain).
6
CD had begun studying bloom (the epicuticular 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 (notes in 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).
7
CD had mentioned his observations on the behaviour of leaves of Desmodium and Cassia throwing off water in a letter to Müller of 14 May 1877 (Correspondence vol. 25). He had asked Müller to make similar observations on any sensitive species of Mimosa. In Movement in plants, p. 128, CD had noted that leaves of Cassia, though not sensitive to touch, partially assumed their nocturnal position if shaken or syringed with water. He also noted movement in terminal but not lateral leaflets of Desmodium gyrans (a synonym of Codariocalyx motorius, telegraph or semaphore plant) when syringed (ibid., p. 363).
8
Müller had mentioned that bees of the genera Trigona and Melipona were attracted by the bright yellow pollen of flowers of Lagerstroemia, while ignoring the less noticeable green pollen (letter from Fritz Müller, 7 February 1881).

Manuscript Alterations and Comments

0.1 (Railway … S.E.R.)] parentheses added
2.4 in this family 2.5] above del ‘here’
3.2 (if … publishing)] interl
3.2 use] ‘us’ over ‘m’
3.4 suspect] above del ‘believe’
4.5 kind] after del ‘on’

Please cite as “DCP-LETT-13113,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-13113