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Darwin Correspondence Project

To Francis Darwin   2 July [1878]1

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

July 2d

My dear F.

Murie has written to me & you, asking me if you were away to look over your revise, which I have done & found nothing to correct & no criticism to make to you, except that one or two sentences might have been clearer.2 The whole strikes me as excellent & conclusive.— The revise is marked “25 copies”: had you not better get more?—

I have sent cheque to a repeated bill from Griffin for 2.10.10— A thermometer has come from Kew, for which I have also paid,— I think 1.11.0.—3 There is a “certificate” with the thermometer.—

I will now go through your letter, but first will say that Bernard seems quite well, though temper not quite so placid as formerly. He has just started very happy & eager in “boobo” with Miss Darcy & Bessy to the Station.4

I think you certainly had better call on Semper; you can say that I asked you to do so to give my very kind remembrances. You know that he has lately returned from America—has travelled much in Philippines & Malay Arch.—has worked on same subjects as Balfour—is a first-rate man, & I liked him, but he is said to have bad temper & to think that everyone is depreciating him.— He dedicated a magnificent essay to me on eyes of a Mollusc,— Onchidium.—5

I have written to Kew about Porliera: do the leaves look like silver under water? Can they shut up to check evaporation; something of this kind occurs (Duval-Jouve) with certain grasses: you could try (if you could get permission) by enclosing small branch in well wetted bottle with wet sponge.—6

I am glad to hear that Sachs tries “fools experiments”.

Do what you think fit about the 10£ Telescope, & any other instrument; only do not waste money, as you know your honoured father hates this.7

I go on maundering about the pulvinus, cushion or gland whichever you call it, & from what I have seen roughly in the petioles of the Cotyledons of oxalis, I conclude that a pulvinus must be developed from ordinary cells, which secrete water into the inter-cellular spaces on the concave side of a bending organ; & that a pulvinus is developed only when the bending has to be continued for a period after growth has ceased or nearly ceased.8

The cotyledon of Oats bending towards light would, I think, do for observation, & I much wish that you wd. try either there or here whether by cutting thin sections about 110th. of inch above the soil of 2 or 3 cots:, you could measure under high power the diameter of the cells, & observe whether their diameter is the same all round. If you can ascertain their average diameter, then cut sections on the most bent part, at same height above soil as before, & see if cells on concave side of the stem where bent through heliotropism (or apogeotropism) are smaller than those on convex side.9 I cannot remember whether such observations have been made, but I think that they are worth making. If there is no such action, as I imagine how the deuce can a pulvinus be developed in all sorts of Families?

I am trying a slight modification of your dodge; & putting night-light under large bell-glass, standing on little wooden bricks to let some air come in, & I have succeeded in keepin jar of water for many hours between 75° & 80° F:10

I have thanked Murie & returned revise.11


The year is established by the relationship between this letter and the letter from Francis Darwin, [29 June] 1878 (see n. 5, below).
James Murie was assistant secretary of the Linnean Society; he sent proofs of Francis Darwin’s revised version of a paper on the nutrition of Drosera rotundifolia (common or round-leaved sundew) that he had presented at a meeting of the society in January (F. Darwin 1878a). Murie’s letter has not been found.
CD’s Account books–cash account (Down House MS) records a payment of £2 10s. 10d. to Griffin for ‘Chemical Apparatus’; J. J. Griffin & Sons were London scientific-instrument suppliers and publishers in London. There is no record of a payment for the thermometer.
Mary Catherine Georgiana D’Arcy had arrived at Down House on 1 July 1878. She and Elizabeth Darwin left Down for London on 2 July; Elizabeth was going to stay with her sister, Henrietta Emma Litchfield. (Emma Darwin’s diary (DAR 242).) Bernard Darwin was 22 months old; he called a vehicle of any sort a ‘boo boo’ (see letter to G. J. Romanes, 16 June [1878]).
Francis had asked whether he should call on Carl Gottfried Semper (see letter from Francis Darwin, [29 June] 1878). Semper had dedicated his book on the visual organs of the vertebrate eye type on the backs of sea slugs to CD (Semper 1877b). In July 1877, before Semper departed for America, he sent CD a copy (Correspondence vol. 25, letter from C. G. Semper, 13 July 1877). Onchidium is a genus of air-breathing marine slugs (pulmonate gastropods) in the family Onchidiidae. Semper had explored the Philippines from 1858 to 1865; he contributed two volumes of a ten-volume work on the fauna of the Philippine archipelago (Semper et al. 1868–1916, vols. 1 and 3). Francis Maitland Balfour was lecturer on animal morphology at Cambridge University.
CD had asked Joseph Dalton Hooker whether he could borrow a plant of Porlieria hygrometrica from Kew (letter to J. D. Hooker, 1 July 1878). Francis had described the plant as almost always being asleep (letter from Francis Darwin, [22 June 1878]). Joseph Duval-Jouve had discovered the cellular mechanism by which certain grasses rolled up or folded their leaf-blades inwards to prevent moisture loss (Duval-Jouve 1875, pp. 326–9).
Julius Sachs’s ‘fool’s experiment’ and the purchase of a micro-telescope had been mentioned in the letter from Francis Darwin, [22 June 1878].
CD described ‘a so-called joint, cushion or pulvinus’ as consisting of an aggregate of small cells that had ceased to increase in size from a very early age (Movement in plants, p. 2). In plants with leaves attached to the stem by a petiole or leaf-stalk, the pulvinus is located at the base of the leaf-stalk. CD was investigating when the organ emerged, and whether there was a pulvinus in cotyledons. He later discussed the emergence of pulvini and variations in cell length in Oxalis corniculata in Movement in plants, pp. 119–21.
For CD’s understanding of the nature of the cotyledon in grasses, see Movement in plants, p. 62. Grass leaves do not have a stalk but are sessile, and their pulvini are located in the leaf-sheath, the portion of the leaf that encircles the shoot or stem. Apogeotropism: the tendency of leaves and other parts of plants to turn away from the earth and bend in opposition to gravity (OED).
CD was probably trying to determine the conditions under which radicles turned towards or away from water; he wished to understand the differences in the experimental results obtained by Julius von Sachs and Theophil Ciesielski (see letter to Francis Darwin, [13–26 May 1878]). The letter in which Francis described his ‘dodge’ has not been found.
CD’s letter to Murie has not been found. See n. 2, above.


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

Duval-Jouve, Joseph. 1875. Histotaxie des feuilles de graminées. Annales des sciences naturelles (botanique) 6th ser. 1: 294–371.

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

OED: The Oxford English dictionary. Being a corrected re-issue with an introduction, supplement and bibliography of a new English dictionary. Edited by James A. H. Murray, et al. 12 vols. and supplement. Oxford: Clarendon Press. 1970. A supplement to the Oxford English dictionary. 4 vols. Edited by R. W. Burchfield. Oxford: Clarendon Press. 1972–86. The Oxford English dictionary. 2d edition. 20 vols. Prepared by J. A. Simpson and E. S. C. Weiner. Oxford: Clarendon Press. 1989. Oxford English dictionary additional series. 3 vols. Edited by John Simpson et al. Oxford: Clarendon Press. 1993–7.


Suggests FD call on Carl Semper.

Inquires about Porlieria: Do the leaves shut to check evaporation? Does it appear silver under water?

Explains how he thinks the pulvinus acts; wishes FD would investigate the point.

Letter details

Letter no.
Charles Robert Darwin
Francis Darwin
Sent from
Source of text
DAR 211: 32
Physical description
AL inc

Please cite as

Darwin Correspondence Project, “Letter no. 11586,” accessed on 15 April 2024,