# From Francis Darwin   [21 July 1878]1

Bot Institut | Würzburg

Sunday

My dear Father,

Many thanks for your long letter which is very interesting & told me all I wanted.2 I have been going on a twiners a bit, & I think the movement is certainly worth carefully working at. I believe you are right that nutation goes on in the free tip. I have been tracing it, like this, putting a bell glass with cylindrical sides over the shoot, & tracing the course by Pouters3 dodge of a square edge, the curve is not a simple spiral, but something like this, going on the whole spirally up but with distinct backward & downward moves, showing that all sides must be growing; I made a curve on a bell glass of a Cobaea tendril which was nutating & making one circle in an hour & it showed fine modified nutation; when it was at one end of its big circle it made 3 little clear circles each in $\frac{1}{4}$ hr & then swept across in a continuous line to make a big one again.4 I have read Wiesner’s thing & should not have had a glimmer of an idea of what it meant. Sachs says induction is the same as Nachwirkung or after effect.5 As far as I can make out he means that if a straight shoot is exposed to light on one side for a time it will bend to AC, then if the light is removed it will go on curving as AD, then if the light is brought back it will not curve more like AE but go on in the old direction— Sachs thinks very little of it he says Wiesner writes over again with much parade what is quite well known already; but Sachs is certainly severe. I must read de Vries on Epinastie & Hyponastie & I will see what Sachs says.6

I am afraid Gossypium does not sleep or any how very slightly.7 I made a mistake about Bauhinia Richardeana it has only a much divided leaf like the other species. Also I gave a name wrong it is Albizzia Zulibrissin.8 Here are a few more Leguminosæ

Pterolobia abyssinica shuts upwards

Cassia suffruticosa & tomentosa

Poinciana gillesia   upwards

Prosopis juliflora   upwards

Coulteria pertinata   upwards

Adenanthera pavonina— slight sideways twisting of leaves

The Adenantheras seem the only slightly new movement,

Albizzia Lebek9

It seems to me also that it cannot be growth or increased tension on the outer side. of a tendril, but that shortening of the inner side is the primary cause & the outer side lengthens to allow the tendril to curl up— When a tendril finds it cannot catch anything it curls up, but it would never be such an idiot as to grow violently on one side when it has no object to gain; but supposing that while it keeps itself straight it is doing work, as it were against a spring, then it would be quite natural that it should allow the spring to do what it liked when there was no object to be gained by keeping the spring stretched. I don’t see how they can distinguish between the stretching of the outer convex side & its growth. I kept Porliera in the pot for 3 or 4 days without water & the leaves were then certainly slightly shut in the morning, I then watered it & the next morning they were wide open   I will water the bed plant well.10

I will look out for some other sleepers.

Semper said he should not order the machine yet as it was a large sum for him; he showed me all over his laboratory & was very pleasant & awfully civil11   He has lots of living creatures & a corresponding smell, young alligators & prairie dogs, & birds—& a fine aquarium with lots of axollotls & menobranchus & blind things from Carniola &c.12 He doesn’t think much of Weismann’s experiments it seems to me that no German thinks much of other scientific men.13 Semper has a fine case of changed conditions producing an effect a Menobranchus? can be made to lay eggs just like a machine, if kept for some months in a small aquarium with few plants & then put into a large one with plenty of plants, though fed well in both cases. He has several of those great spiders (Mygales?) which seem well, he says they eat mice.14

I shall leave here about Aug 8th I expect & I shall be awfully glad to get back

Your affec son | Frank Darwin.

Sachs has just shown me the fruit of Helvingia ruscifolia nearly related to Ivy, the petals are fleshy, purple, & full of juice like a mahonia berry, & close over the carpels so that the thing looks like a berry, it has a most beautiful bloom, it seems to me a fine case of bloom appearing on petals when they act the part of fruit. I will clean some & see if they burst in water15

## CD annotations

0.2 Sunday] crossed ink; ‘July 21— 1878’ ink
1.1 Many thanks … wanted. 1.2] crossed ink
1.9 it showed … again. 1.12] double scored pencil
2.1 I am … Leguminosæ 2.4] crossed pencil; opening square bracket pencil
4.1 Cassia suffruticosa & tomentosa] circled pencil; ‘[let]added pencil
11.6 quite natural … other sleepers. 12.1] crossed blue crayon
11.9 Porliera … well. 11.12] opening square bracket pencil, closing square bracket blue crayon
13.1 Semper … to get back 14.1] crossed pencil
13.1 Semper … for him;] scored blue crayon; ‘Bloom’ added blue crayon
16.1 Sachs … in water 16.5] double scored pencil
Top of letter: ‘Sleeping Plants | Porliera | Helvingia, thick petals with bloom. | Wiesner on Light’ ink
End of letter: ‘Bloom’ red crayon underl red crayon

## Footnotes

The date is established by CD having crossed out ‘Sunday’ and written in ‘July 21— 1878’ (see CD annotations).
Pouter was Leonard Darwin’s nickname.
Cobaea is a subtropical genus of the family Polemoniaceae (phlox). CD had discussed Cobaea scandens (cup and saucer vine) in Climbing plants 2d ed., pp. 106–11.
CD had been puzzled by Julius Wiesner’s description of heliotropism and gravitropism as ‘induction phenomena’ and had asked Francis to see whether Julius Sachs could explain his meaning (see letter to Francis Darwin, 17 July [1878] and n. 5).
Hugo de Vries used the terms hyponasty and epinasty to denote the greater longitudinal growth along the lower or upper side of a plant part that caused upward or downward bending respectively (Vries 1872, pp. 252–3); CD had asked Francis to discuss these movements with Sachs (see letter to Francis Darwin, 14 July [1878]).
Francis had initially thought that Gossypium (cotton) might sleep; CD considered this would be valuable if true (see letter from Francis Darwin, [12 July 1878], and letter to Francis Darwin, 14 July [1878]).
Francis had described Bauhinia richardiana as having two large leaflets (letter from Francis Darwin, [12 July 1878]) and had referred to Albizia julibrissin as Albizia Zulu brizzia (letter from Francis Darwin, [before 17 July 1878]).
Pterolobium abyssinicum is an unresolved name; Pterolobium is the genus of redwing. Cassia suffruticosa is a synonym of Senna surattensis ssp. surattensis; C. tomentosa L. is a synonym of Senna multiglandulosa. Poinciana gilliesii is a synonym of Caesalpinia gilliesii (bird-of-paradise shrub). Prosopis juliflora is a species of mesquite. Coulteria pertinata is an unknown combination; Francis may have intended Caesalpinia pectinata, a synonym of Coulteria tinctoria and Caesalpinia spinosa (tara). Adenanthera pavonina is the red beadtree. Albizia lebbeck is the woman’s tongue or siris tree.
See letter to Francis Darwin, 17 July [1878] and n. 4. In the Würzburg garden the Porlieria specimen planted in the ground typically slept during the day, but had opened after heavy rain; the potted specimen, always well-watered, kept its leaves open (see letter from Francis Darwin, [after 7 July 1878] and n. 3).
Carl Gottfried Semper had received information about where to buy a typewriter like CD’s, but had not yet received CD’s offer of his own machine as a gift (letter to C. G. Semper, 19 July 1878). Semper was professor of zoology in Würzburg.
The axolotl is Ambystoma mexicanum. Menobranchus is a former genus roughly equivalent to Necturus (mudpuppies and waterdogs). Both are within the order Caudata, salamanders. CD mentioned the caves of Carniola in Origin 3d ed., p. 154. Andrew Murray had provided CD with information and references on the Carniola caves (see Correspondence vol. 8, letter from Andrew Murray, 3 May 1860, and Origin 3d ed., p. 156).
August Weismann was professor of zoology at Freiburg im Breisgau. In his essay ‘Ueber die Umwandlung des mexicanischen Axolotl in ein Amblystoma’ (On the transformation of the Mexican axolotl into an Amblystoma; Weismann 1875b), Weismann argued that the apparent metamorphosis of some axolotls (which were then classified as Siredon mexicanus) into the salamander Amblystoma (a synonym of Ambystoma) was due to reversion caused by adaptation to conditions different from their normal high-altitude, deep-water environment. Weismann stressed that all evidence showed that axolotls never transformed in their natural environment (Weismann 1875b, pp. 303–4).
Mygale is a former genus that included most mygalomorph spiders; some of the larger mygalomorph spiders such as Theraphosa blondi (Goliath birdeater) eat mice.
Francis and CD had been investigating the function of bloom on leaves for much of the year (CD’s ‘Journal’ (Appendix II)). Helvingia rusciflora is a synonym of Helwingia japonica; the flowers are epiphyllous, growing from the midrib of the leaf blade. The genus of ivy is Hedera; both Helwingia and Hedera were placed in the family Araliaceae (see Bentham and Hooker 1862–83, 1: 931–47); for modern systematics of Helwingia, see Ao and Tobe 2015. Mahonia is the genus of Oregon-grape, now often placed in synonymy with the closely related genus Berberis.

## Bibliography

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

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 28 vols to date. Cambridge: Cambridge University Press. 1985–.

Origin 3d ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 3d edition, with additions and corrections. By Charles Darwin. London: John Murray. 1861.

Vries, Hugo de. 1872. Ueber einige Ursachen der Richtung bilateralsymmetrischer Pflanzentheile. Arbeiten des botanischen Instituts in Würzburg 1 (1871–4): 222–77.

## Summary

Has been investigating nutational movements of climbing plants; comments on the opinions of Julius von Wiesner and Julius Sachs. Remarks on the sleep movements of certain plants and the mechanism of tendril curvature. Is experimenting with Porlieria.

Has visited K. G. Semper’s laboratory.

## Letter details

Letter no.
DCP-LETT-11623
From
Francis Darwin
To
Charles Robert Darwin
Sent from
Botanisches Institut, Würzburg
Source of text
DAR 162: 59, DAR 209.8: 151
Physical description
ALS 6pp †