From Francis Darwin   [12 July 1878]1

Botanisches Institut

My dear Father

I cut sections of an oat 3 mm above the ground & it was about as green as the 5 mm one. Sachs couldn’t exactly say whether it could assimilate, but it would want light to fully develope its chlorophyll just as much as it wants light to make starch out of its perfect chlorophyll.2

I have been round the hot houses & plants out side 2 or 3 times & have found some sleepers we have not had, but no new principle—3 I will look at them all again & describe them better to you.

Cassia baccata 4 leaflets which turn outside in like our Cassia

Adenantha pavonina (Legumin) Leaflets drop & turn edgwise ie not quite outside in—
Tamarindus indicus— leaflets shut upwards
Bauhinia Richardiana (Leg) 2 large leaflets—drop
Ligophyllum Guaiacum— has joints & ought to shut like Arachis but is v. unhealthy
Indigofera tinctoria } leaflets drop simply
  "   Tejsmanni
Edwardsia chrysophylla sleeps like Mimosa but I dont know whether 2ndy petioles close up.
Albizzia lophantha I think we had only the generic name was different. It sleeps pretty much like Mimosa
Oxalis floribundus } like Acetosella
—"— Regnilli

also O vespertilionis which has odd leaflets so

diagram

O rusciformis has leaflike foot-stalks but no little leaves at the end   I am not sure yet whether it sleeps.4

I am nearly sure Gossypium sleeps, simply dropping the leaf downwards— several more Acacias & Coesalpinas I have only seen in the day.5

Besides my wood experiments which are rather failures but now today I have at last got a good method Sachs has set me at climbing plants he wants to prove that tendrils & twisters behave in the same way— But I must write you a letter about that alone   He thinks de Vries has not cleared everything up— The fact is as Sachs says himself Sachs has never worked at twiners himself & has not thoroughly gone into the mechanical problems6

Please thank Bessy for her very nice letter—& tell her & mother I will write a real letter tomorrow7

Yr affc son | F Darwin

☞ Please send me the address of the American Printing Machine   Semper has writers palsy in his right hand & thought they cost more than £20 or he would have got one before.8

CD annotations

1.1 I cut … chlorophyll. 1.4] crossed ink; ‘Copied’ added ink; enclosed in square brackets blue crayon
2.1 I have … outside in like 3.1] crossed pencil
3.5 Bauhinia … drop] crossed pencil
3.8 Indigofera tinctoria] scored pencil
3.9 Tejsmanni] scored pencil
3.12 Albizzia lophantha] ‘ = Acacia’ added pencil
6.1 Besides … F Darwin 8.1] crossed pencil; ‘9 33 – 12–6 | 51 [‘1’ over ‘0’] 14’ pencil
9.1 Please ... before. 9.3] crossed blue crayon
Top of letter: ‘Chlorophyll in seedlings & Sleep of Plants | July 12[‘2’ over ‘0’]th 1878’ pencil; ‘Light | & | Sleep’ blue crayon
1
The date is established by CD’s copy of the first paragraph of this letter, labelled ‘Frank July 12th 1878’, in his notes (DAR 209.7: 158).
2
The cotyledon of oats that Francis had previously examined had yellow chlorophyll; Julius Sachs had concluded the chlorophyll was not fully developed. See letter from Francis Darwin, [after 7 July 1878].
3
By ‘no new principle’ Francis probably means that he has not found a plant whose sleep movements differ in any way from those of plants that he has already mentioned.
4
Cassia baccata is an unknown combination. ‘Our Cassia’ may refer to Cassia neglecta (a synonym of Senna neglecta), a species that CD had studied in June 1878 (notes dated 9–14 June [1878], DAR 209.6 41–5). Adenanthera pavonina is the red beadtree (‘Adenantha’ is a misspelling). Tamarindus indicus (a synonym of Tamarindus indica) is tamarind. Ligophyllum guaiacum is an unknown combination; the genus Guaiacum is in the family Zygophyllaceae (caltrop). Indigofera tinctoria is true indigo; I. teysmannii is a synonym of I. zollingeriana (Zollinger’s indigo). Edwardsia chrysophylla is a synonym of Sophora chrysophylla (mamani). Albizia lophantha is a synonym of Paraserianthes lophantha (plume albizia); Francis may have known it as Acacia lophantha, another synonym. Mimosa is the genus of sensitive plants. Oxalis floribunda (‘floribundus’ is a misspelling) is abundant flowering wood sorrel; O. regnellii is a synonym of O. triangularis subsp. papilionacea (purple shamrock); O. acetosella is a synonym of O. montana (mountain wood sorrel); O. vespertilionis is a synonym of O. violacea (violet wood sorrel); Oxalis rusciformis (a synonym of O. fruticosa subsp. fruticosa) is winged oxalis.
5
Gossypium is the genus of cotton; Francis’s notes on sleep in G. maritimum and G. brasilense (both synonyms of G. barbadense, Creole cotton) are in DAR 209.14: 33. Caesalpinia is the genus of nicker and poinciana. The genus Acacia as it was defined at this time is now often split into five related genera: Acacia (mostly limited to Australian species), Vachellia, Senegalia, Acaciella, and Mariosousa (see Bouchenak-Khelladi et al. 2010).
6
Francis was testing the elasticity of wet and dry wood (see letter from Francis Darwin, [before 7 July 1878]). CD had acknowledged Hugo de Vries’s work on climbing plants in the second edition of Climbing plants, and endorsed De Vries’s conclusion that twining stems were not irritable whereas tendrils were (Climbing plants 2d ed., pp. 16–17, 170–1, and 204).
7
Neither Elizabeth Darwin’s letter to Francis Darwin nor Francis’s letter to Elizabeth and Emma Darwin has been found.
8
CD had purchased a typewriter in 1876; it cost £21 (Correspondence vol. 24, letter from Francis Darwin, [1 May 1876] and n. 4). Carl Gottfried Semper was professor and director of the Zoological Institute in Würzburg. Writer’s palsy was a term that emerged in the mid nineteenth century to describe the spasm or cramp that resulted from excessive use of the muscles of the hand due to writing (OED).

Please cite as “DCP-LETT-11604,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11604