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Darwin Correspondence Project

From Francis Darwin   [6 July 1879]

I have been talking about the sieve experiment. It all depends on getting the right degree of dampness of the surrounding air— Phaseolus are said to act well, I will try it here with his sieve in the same place where he does it.1 At Down I failed with Faba but succeeded with Lepidium.2 I am v glad you approve so much of the bean experiment with caustic above & below.3 The air roots dont bend at all even without caps of any kind. I will try caps on Chlorophytum roots in water they are good strong roots.4 It has turned so horribly cold I have put on thick things, & the plants are not growing a bit well

Many thanks for Ubbadubba news.5 | F.D

Will mother tell Bessy I have written today to the Riffel6


See letter to Francis Darwin, 4 July [1879]. Francis performed experiments to determine the sensitivity of the tip of the radicle to damp air; one of the species tested was Phaseolus multiflorus (a synonym of P. coccineus, scarlet runner-bean). CD described the protocol devised by Julius Sachs (Sachs 1872a, p. 212), in which sieves with seeds germinating in damp sawdust were suspended so that the bottom was inclined at 40° to the horizon, and the tips of the radicles were coated to exclude moisture, in Movement in plants, pp. 180–2.
Francis refers to Vicia faba (broad bean) and Lepidium sativum (garden cress). In his letter of 4 July [1879], CD had mentioned he had forgotten which species he and Francis had already tested.
See letter from Francis Darwin, 4 July 1879 and nn. 3 and 6. Plants of Chlorophytum (the genus of spider plants) have aerial roots.
See letter to Francis Darwin, 4 July [1879]. Ubbadubba was a pet name for Bernard Darwin, Francis’s son.
The Riffelhaus, a hotel built in 1853, is near Zermatt in the Swiss Alps. Elizabeth Darwin was on holiday in Switzerland with Mary Elizabeth Atkin; they arrived at the hotel around 10 July 1879 (letter from Emma Darwin to W. E. Darwin, [10 July 1879] (DAR 219.1: 124)).


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

Sachs, Julius. 1872a. Ablenkung der Wurzeln von ihrer normalen Wachsthumsrichtung durch feuchte Körper. Arbeiten des Botanischen Instituts in Würzburg 1 (1871–4): 209–22.


Describes bean experiments. Will tell Emma Darwin to tell Elizabeth Darwin that he has written to the Riffel.

Letter details

Letter no.
Francis Darwin
Charles Robert Darwin
6 7 79
Source of text
DAR 274.1: 61
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 12296F,” accessed on 22 September 2023,