# To Francis Darwin   17 July [1878]1

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

July 17th

My dearest F.

Before answering your long letter, there are a few miscellaneous points to touch on.—2 You audacious dog I have answered about Printing machine without the aid of red-pencil &c.— I rather hope you will feel inclined to give it to Semper.3

I have got branch of Porliera with Quick-lime, & fancy it has produced very slight effect. Your rain-case with Porliera is capital: when leaflets are asleep about $\frac{2}{3}$ of under surface is protected or covered by next leaflet behind, & I imagined that perhaps there wd be very few or no stomata in the unprotected part.—4

In the proceeding of K. Akad. d. Wissenschaften in Wien. In No XVI just received there is long abstract of great Paper or book by Wiesner on Heliotropism & Geotropism: it seems very important, but I cannot understand it; do get it at Wurzburg & read it; my puzzle is at p. 139, what on earth he means by “Induction”.— Perhaps Sachs will have read it— After you have read it; if you do not understand talk to him about “Induction”.—5

I have nearly finished with Thalia— it is a wonderful case, but not worth the time which I have spent on it; as I now find through Dyer that Delpino has described an allied genus, but seems to have entirely missed the interesting point of sensitiveness.—6

I partially agree with what Sachs says about the distinction between the circumnutation of free twiners, & the subsequent growth on one side after they have twined round a support; that the growth then is almost exclusively on one side alone is, I think, shown by their clasping the stems very closely; but they slide a little up the support in their coiled state which seems to show that there must be a little growth on all sides.— Nor can I see why the part beyond point of contact shd at once stop circumnutating. This seems well worth investigating.— There is nothing about this, I believe, in my book, except the fact of sliding up, & I had not thought of it in relation to our general view of modified circumnutation.— At p. 131 of 2d Edit there is the passage about circumnutation of tendrils stopping when apogeotropism comes into action; but you must remember that I there speak only of conspicuous circumnutation.7 Lately I have observed several plants; laid on one side for apogeotropism to act carefully by tracing, & the line is sometimes quite straight, but more commonly slightly zig-zag, showing a vestige of circumnutation, just as with Heliotropism.

At—p. 129 of Climbing book there is fine case of modified circumnutation in order for tendril to pass over terminal shoot.8

I never tried turning a twined plant upside down; so your fact new to me.—9

I told De Vries the case about tips of tendrils (p. 132) was well worth investigating in relation to growth, & he seemed to agree.—10

The contraction of tendril into spire, which is so important for the plant, seems another case of modified circumnutation or rather, I suppose, of growth prolonged on one side alone after it has ceased on all other sides.— I cannot believe that a tendril curling when touched in less than 1m. is due to growth; & De Vries seemed in a letter to me staggered by my arguments.11

You must remember when I wrote the 1st Edit. of Climbers, I knew very little about growth or cause of circumnutation. I do not know whether I have answered what you want to know, & whether this note will be intelligible. You have given me fine list of Sleepers.12

It is very odd about wet & dry culms of grass & sticks: does Sachs understand it.—13

Something made me think the other day that aggregation in roots from C. of Ammonia, wd be in your line & wd. be fine subject: a little wild Euphorbia showed it plainest, & a wonderful phenomenon it was.—14 I wonder no one has taken it up.

Bernard gets more & more charming: he rebuked me sternly yesterday, because I said he was going in a booboo, whereas I ought to have said a gee-gee.—15

Dearest old Backy | C. D.—

I fear this letter will bother you to read.

## CD annotations

3.3 do get it … earth 3.4] scored red crayon
3.4 “Induction”.— 3.5] underl red crayon
5.4 but they … support 5.5] underl red crayon
5.5 coiled state] underl red crayon

## Footnotes

The year is established by the relationship between this letter and the letter from W. T. Thiselton-Dyer, 16 July 1878 (see n. 6, below).
See letter from Francis Darwin, [before 17 July 1878] and n. 10. CD’s letter, in which he suggested that his typewriter be sent to Carl Gottfried Semper as a gift, had evidently crossed in the post (letter to Francis Darwin, 14 July [1878]).
Quick-lime or calcium oxide is a drying agent. CD’s specimen of Porlieria hygrometrica moved differently from plants in Würzburg (see letter to Francis Darwin, 14 July [1878] and n. 3). Francis had reported that the P. hygrometrica specimen in the Würzburg garden had slept during the day, but had opened after heavy rain. He further noted, having compared the Würzburg plants with a twig sent by CD, differences in the arrangement of leaflets, leading him to question whether they were observing the same species (see letter from Francis Darwin, [after 7 July 1878]). Francis had been unsure of what CD wanted him to observe with respect to the stomata (see letter from Francis Darwin, [before 17 July 1878] and n. 8).
The first part of Julius Wiesner’s monograph on heliotropic phenomena in the plant world (Wiesner 1878–80) was presented on 4 July 1878 at the Imperial Academy of Sciences in Vienna; an abstract appeared in Anzeiger der Kaiserlichen Akademie der Wissenschaften in Wien 15 (1878): 137–40. Wiesner called heliotropism (and gravitropism) induction phenomena because the response to a directional light source continued for a time even after the source was removed, in the absence of any counteracting force. The abstract stated that Wiesner had demonstrated that heliotropism was an induction phenomenon and that the effects induced were determinate and not additive (i.e. each stimulus resulted in a specific response). Francis was working in Julius Sachs’s laboratory in Würzburg.
See letter from W. T. Thiselton-Dyer, 16 July 1878 and n. 7. Federico Delpino had described the floral morphology of another genus of the family Marantaceae, Maranta, in Delpino 1869; CD had been instrumental in getting this article translated into English and published in Scientific opinion (Correspondence vol. 18, letter from Federico Delpino, 28 February 1870; Delpino 1870). Delpino discussed Thalia dealbata (powdery alligator-flag) in Delpino 1870, pp. 135–7. For CD’s observations on the sensitivity of the pistil in T. dealbata, see the letter to Francis Darwin, 7 [July 1878], the letters to G. H. Darwin, 10 [July 1878] and 11 [July 1878], and the letter to W. T. Thiselton-Dyer, 14 July [1878].
Francis had reported Sachs’s views on movement in climbing plants in his letter of [before 17 July 1878]. CD refers to Climbing plants 2d ed., p. 131. Apogeotropism is directional movement away from the ground, in opposition to gravity.
Climbing plants 2d ed., p. 129; the terminal shoot is the main branch.
Francis had observed that the last turn of a twining plant would unwind if the plant were turned upside down (letter from Francis Darwin, [before 17 July 1878]).
Climbing plants 2d ed., p. 132. For Hugo de Vries’s response to CD’s observations on tendrils, see Correspondence vol. 23, letter from Hugo de Vries, 7 November 1875 and n. 6.
The first edition of Climbing plants was published in 1865. For the lists of sleeping plants, see the letters from Francis Darwin, [12 July 1878] and [before 17 July 1878].
CD had described the effect of carbonate of ammonia on Euphorbia in Insectivorous plants, pp. 63–4. He later discussed the possible cause of the phenomenon in the letter to F. J. Cohn, 2 September 1875 (Correspondence vol. 23).
Bernard Darwin had earlier used the word ‘booboo’ for a vehicle of any sort (see letter to G. J. Romanes, 16 June [1878]). A gee-gee may have been Bernard’s word for a horse-drawn vehicle.

## Bibliography

Climbing plants 2d ed.: The movements and habits of climbing plants. 2d edition. By Charles Darwin. London: John Murray. 1875.

Climbing plants: On the movements and habits of climbing plants. By Charles Darwin. London: Longman, Green, Longman, Roberts & Green; Williams & Norgate. 1865.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Delpino, Federico. 1870b. Brief remarks on the biology and genealogy of the Marantaceæ. Scientific Opinion 3: 111–12, 135–7.

Insectivorous plants. By Charles Darwin. London: John Murray. 1875.

Wiesner, Julius. 1878–80. Die heliotropischen Erscheinungen im Pflanzenreiche. [Read 4 July 1878 and 18 March 1880.] Denkschriften der kaiserlichen Akademie der Wissenschaften, mathematisch-naturwissenschaftliche Classe 39 (1879) pt. 1: 143–209; 42 (1880) pt. 1: 1–92.

## Summary

Discusses sleep movements of Porlieria.

Has read an abstract of Julius Wiesner on heliotropism and geotropism ["Die heliotropischen Erscheinungen im Pflanzenreiche", Anz. Kais. Akad. Wiss. Wien 15 (1878): 137–40] which seems important but is puzzling.

Gives details of his observations on climbing plants with reference to comments by Julius Sachs.

## Letter details

Letter no.
DCP-LETT-11615
From
Charles Robert Darwin
To
Francis Darwin
Sent from
Down
Source of text
DAR 211: 37
Physical description
8pp †

## Please cite as

Darwin Correspondence Project, “Letter no. 11615,” accessed on 8 March 2021, https://www.darwinproject.ac.uk/letter/DCP-LETT-11615.xml

letter