From Francis Darwin   [29 June] 18781

Hôtel de Rassie | Würzburg

Sat 28th/78

My dear Father,

I shall have lots of time to do the oats & will sow some next week.2 Also I can easily see about sleepers. Porliera hygrometrica is the plant & belongs to the Zygophylleæ.3 There is something odd about it I found that a twig in water in the room was open while the plant in the garden was shut, & it does not depend on light only as a twig kept under water in a glass & in blazing sun, was quite open. I have seen a few plants that look as if they must sleep & I will go round the garden carefully in the evenings when I always go a loaf.

I think the great distinct Pfeffer makes is between sleepers with joints & those without joints, & says that there is no growth but only variation in tension in those that have joints. But Batalin says there is very slight growth even in those with joints.4 It seems an absurd thing to call the two really different. I will see what Sachs5 says. If possible I will do the microscoping here. I have been cutting sections of roots to see the development of secondary roots & I shall know enough to make out the anatomy of the bean roots if it is wanted. Today I did the male & female organs of Marchantia6 & tried the prothallus of a fern but failed, the great thing is not so much very thin sections, but

⁠⟨⁠at least 2 pages missing⁠⟩⁠7

like this

diagram

so that they move up not down at night8

I must leave off & measure my roots9

Your affec | F D

(ought I to call on Semper?)10

incomplete

CD annotations

1.1 I shall … sections, but 2.8] crossed blue crayon
1.2 Porliera hygrometrica] ‘Sapindaceæ’ interl pencil
End of letter: ‘Porliera— Branch growing vertically down—’ ink; ‘Add Ipomœa to list if not done see note on Pisum.’11 pencil
1
The date is established by the relationship between this letter and the letter to Francis Darwin, 26 June [1878]. In 1878, the Saturday following 26 June was 29 June. Francis evidently dated the letter 28 June in error.
3
See letter from Francis Darwin, [22 June 1878] and n. 6, and letter to Francis Darwin, 26 June [1878] and n. 5. Porliera hygrometrica is considered a doubtful species and is possibly a synonym of Porlieria hygrometra, in the family Zygophyllaceae.
4
See letter to Francis Darwin, 26 June [1878] and n. 7. Wilhelm Pfeffer had countered the claim made by Alexander Fedorovich Batalin that a small amount of growth occurred in the joint (pulvinus) during periodic movements; Pfeffer noted that measurements made with a micrometer confirmed the absence of any growth once the joint regained its original position (see Batalin 1873, p. 455, and Pfeffer 1875, p. 4). See also Movement in plants, p. 113.
6
Marchantia is a genus of liverworts.
7
The extent of the missing text is unknown, but is likely to consist of at least one half of a folded manuscript sheet, since the surviving section of the letter is a torn half of a folded manuscript sheet.
8
The diagram depicts the movements of the leaves of Porlieria hygrometrica; see n. 3, above.
9
Francis had been sectioning bean roots, probably to aid CD in his experiments on movement in the radicles or embryonic roots of beans (Vicia faba; see letter from Francis Darwin, [22 June 1878], and letter to W. T. Thiselton-Dyer, 9 May [1878] and n. 5).
10
Carl Gottfried Semper had dedicated to CD his work on the eyes of sea slugs (Semper 1877b); see Correspondence vol. 25, letter from C. G. Semper, 13 July 1877.
11
The note on Ipomoea (the genus of morning-glories) was probably a reminder to add it to the list of sleeping plants published in Movement in plants, pp. 320–1. For CD’s experiments on Pisum sativum (common pea), see the letter to G. J. Romanes, 16 June [1878] and n. 5.

Please cite as “DCP-LETT-11575,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11575