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Darwin Correspondence Project

To Francis Darwin   [13–26 May 1878]1

My dear Backy—

if you can arrange to stay at home for 3 or 4 days after you return I shall be glad, as I much want you to try a troublesome experiment, of the class Fool.—2 Sachs found that radicles turn to damp surface or water— Ciewenski (or some such name) found exactly the opposite & Sachs is confounded & yet quite believes Ciewenski.—3 Now I suspect that when radicles are hot & dry they may bend to water, but when cold they may turn with disgust from the water; but this seems too good & wonderful a case & too simple an explanation of Sachs perplexity: nevertheless it ought to be tried.—

I do not know at what temp Ciewenski worked so it is a mere guess.—

Work is dull work without you.—

yours affec | C. D.—


The date range is established by the relationship between this letter and the letter from Francis Darwin, [12 May 1878], and by the date of Francis’s return to Down, 27 May 1878 (Emma Darwin’s diary (DAR 242)).
Francis was in Wales visiting the family of his late wife, Amy Darwin, and intended to go on to Cambridge after returning to Down (see letter from Francis Darwin, [12 May 1878] and n. 8).
See letter to Francis Darwin, [11 May 1878] and n. 4). Julius Sachs had referred to Theophil Ciesielski’s observation that roots laid on a horizontal wet surface grew upwards away from the moisture (Ciesielski 1871, p. 33; Sachs 1872, p. 219). Sachs later dismissed Ciesielski’s results, claiming they were due to Ciesielski’s having allowed the roots in his experiments to dry out partially during preparation (Sachs 1873–4, p. 401).


Ciesielski, Theophil. 1871. Untersuchungen über die Abwärtskrümmung der Wurzel. Inaugural-Dissertation welche mit Genehmigung philosophischen Facultät der königl. Universität zu Breslau zur Erlangung der Doctorwürde. Breslau: R. Nischkowsky.

Sachs, Julius. 1873–4. Ueber das Wachsthum der Haupt- und Nebenwurzeln. Arbeiten des Botanischen Instituts in Würzburg 1 (1871–4): 385–474, 584–634.


Has had conflicting information on the movement of radicles; wants FD to experiment with them.

Letter details

Letter no.
Charles Robert Darwin
Francis Darwin
Sent from
Source of text
DAR 211: 26
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 11538,” accessed on 18 May 2021,