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Darwin Correspondence Project

To J. D. Hooker   [8 February 1864]1

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Monday

My dear Hooker

I shall write again.— I write now merely to ask if you have Naravelia (the Clematis-like plant told me by Oliver) to try & propagate me a plant at once.2 Have you Clematis cirrhosa?—3

It will amuse me to tell you why Clematis interests me & why I shd. so very much like to have Naravelia.— The leaves of Clematis have no spontaneous movement nor have the internodes; but when by growth the peduncles of leaves are brought into contact with any object they bend & catch hold. The slightest stimulus suffices, even a bit of cotton thread a few inches long; but the stimulus must be applied during 6 or 12 hours, & when the peduncles once bend, though touching object be removed, they never get straight again.—4

Now mark difference in another leaf-climber, viz Tropæolum; here the young internodes revolve day & night & the peduncles of leaves are thus brought into contact with object & the slightest momentary touch causes them to bend in any direction & catch the object; but as axis revolves they must often be dragged away without catching & then the peduncles straighten themselves again & are again ready to catch.5 So that the nervous system (!!) of Clematis feels only a prolonged touch; that of Tropæolum a momentary touch—the peduncles of the latter recover their original position; but Clematis as it comes into contact by growth with fixed objects has no occasion to recover its position, & cannot do so.6

You did send me Flagellaria; but most unfortunately young plants do not have tendrils; & I fear my plant will not get them for another year; & this I much regret, as these leaf-tendrils seem very curious,7 & in Gloriosa I cd. not make out action; but I have now a young plant of Gloriosa growing up, (as yet with simple leaves) which I hope to make out.—8

Thank Oliver for decisive answer about tendrils of Vines.9 It is very strange that tendrils formed of modified leaves & branches shd. agree in all their 4 highly remarkable properties. I can show beautiful gradation by which leaves produce tendrils: but how axis passes into tendril utterly puzzles me.10 I wd. give a guinea if Vine-tendrils could be proved to be leaves,11

Yours affect.— | C. Darwin

Footnotes

The date is established by the relationship between this letter and the letter from J. D. Hooker, 5 February 1864; in 1864, 8 February fell on a Monday.
Daniel Oliver mentioned Naravelia in his memorandum of [28 January – 8 February 1864]. No evidence has been found that CD ever acquired Naravelia; he only mentioned it briefly twice in ‘Climbing plants’ (pp. 34, 112); see also n. 6, below.
Hooker may have been unable to supply CD with this species. CD described eight other species of Clematis in ‘Climbing plants’, pp. 26–34.
CD may be referring to observations of Clematis flammula and C. vitalba; however, he later discovered slight spontaneous movement in the growing shoots of C. flammula (see ‘Climbing plants’, p. 32, and letter to J. D. Hooker, 5 April [1864] and n. 16). CD’s notes for C. flammula, dated only from April to August 1864, are in DAR 157.1: 73–7; however, another note, dated 1 March 1864, in DAR 157.1: 70 refers to earlier work on C. flammula. For CD’s use of cotton thread that he later weighed to test the sensitivity of Clematis and C. flammula, see ‘Climbing plants’, pp. 27 and 33–4, letter to J. D. Hooker, 5 April [1864] and n. 17, and letter to G. H. Darwin, [after 5 April 1864] and nn. 1 and 3. In ‘Climbing plants’, pp. 32–3, CD mentioned that a C. flammula petiole curled around a stick in 12 hours and did not straighten out again once the stick was removed. The only observational note of CD’s on a Clematis dated before 8 February 1864 was on C. vitalba, and was dated 18 January 1864 (see DAR 157.1: 79); in ‘Climbing plants’, p. 34, CD mentioned that his C. vitalba plants were not healthy but appeared to have similar habits to C. flammula (see also letter to J. D. Hooker, [27 January 1864] and n. 22). CD’s experimental notes on several Clematis species are in DAR 157.1: 62–80), and Clematis is discussed in ‘Climbing plants’, pp. 25–34.
CD is referring to his study of Tropaeolum tricolorum, which he observed in December 1863, January 1864, and on 6 February 1864 (see experimental notes in DAR 157.1: 81–5). CD’s experimental notes on different Tropaeolum species are in DAR 157.1: 81–95; he discussed Tropaeolum species in ‘Climbing plants’, pp. 34–8, with T. tricolorum described on pp. 35–6.
CD’s published comparison of leaf-climbers is in ‘Climbing plants’, pp. 47–8; see also ibid., pp. 111–12. For references to Naravelia, see memorandum from Daniel Oliver, [28 January – 8 February 1864], and ‘Climbing plants’, pp. 34, 112.
See letter from J. D. Hooker, 5 February 1864 and n. 4. CD describes dried specimens of Flagellaria indica in ‘Climbing plants’, p. 46.
CD’s earlier observations of Gloriosa plantii, dated 2 and 24 August 1863, are in DAR 157.1: 108. Observations of the new plant, dated 20 February 1864, 9, 10, 18, and 27 March [1864], and 10 April [1864] are in DAR 157.1: 106–8. He discussed Gloriosa in ‘Climbing plants’, pp. 45–6.
In his memorandum of [28 January – 8 February 1864], Daniel Oliver wrote that vine tendrils were an ‘axial or stem-structure’. CD included Oliver in his thanks to those who provided information and references for ‘Climbing plants’ (see ‘Climbing plants’, p. 14 n.).
A note dated 31 January 1864 in DAR 157.1: 121 discusses the climbing ability of the tendril-bearing Bignonia unguis: This with cases of Gloriosa, Trop. tric. & Clematis makes me strongly suspect that all tendrils are first leaf climbers. Good because genesis of tendrils otherwise inexplicable. N.B. When tendrils formed other leaflets abnormally may be changed. I have seen case in vetch. How is this if botanists are right that some tendrils are stems? For CD’s published conclusions about the gradation from leaf-climbers to tendril-bearing plants, see ‘Climbing plants’, pp. 108–12. He discussed how a leaf came over time to function as a tendril in ‘Climbing plants’, pp. 111–14. See also letter to J. D. Hooker, [27 January 1864] and nn. 19–23.
CD later concluded that vine tendrils were modified flower-peduncles (see ‘Climbing plants’, pp. 79–87, 112).

Summary

Compares Clematis and Tropaeolum with respect to touch response. Tropaeolum shows a momentary response and quick recovery. Clematis takes hours to respond, and shows no recovery.

CD can show the gradations between leaves and tendrils, but how a branch passes into a tendril utterly puzzles him.

Letter details

Letter no.
DCP-LETT-4403
From
Charles Robert Darwin
To
Joseph Dalton Hooker
Sent from
Down
Source of text
DAR 115: 219
Physical description
6pp

Please cite as

Darwin Correspondence Project, “Letter no. 4403,” accessed on 23 July 2019, https://www.darwinproject.ac.uk/letter/DCP-LETT-4403.xml

Also published in The Correspondence of Charles Darwin, vol. 12

letter