To Francis Darwin   22 October 1873

Down

Oct 22 1873

My dear Frank

Thanks for the capital case of inheritance. I want you to do a job for me at Kew, that is if Hooker to whom I will write, can manage it on a Sunday.1 It is to look thro’ the dried collection of Desmodium, and to observe.

(1) whether many of the species bear only 3 leaflets, & the usual relative size of the 2 laterals to the terminal one.—2

(2) I see in Steudel that next to D. gyran is D. gyroides;3 look closely to the leaves of this, and if they are nearly like those of D. Gyrans please to make a plan with compasses, of the length of the main petiole, of the sub-petioles of the leaflets, of the leaflets themselves, & of the large terminal leaflet—

(3) I judge by the names that some of the species are climbers,4 & I want to know whether any bear tendrils. Especially I want to know whether the lateral leaflets have ever been converted into tendrils, whilst the terminal one is still a leaflet: I know of no such case, perhaps Hooker may.

In any species in which the 2 lateral leaflets are very small, observe whether the apex is produced into a free point, as if the leaflet had once existed as a tendril. Take this paper with u as a mem—

& you had better take compasses if you have them.

Yours affection— | Ch. Darwin.

LS(A)

1
CD mentioned Francis’s visit to the Royal Botanic Gardens at Kew, in his letter to Joseph Dalton Hooker of 23 October [1873]. See also letter to Francis Darwin, 10 October 1873.
2
CD discussed the movements and structure of Desmodium gyrans (now Codariocalyx motorius, the telegraph or semaphore plant) in Movement in plants, pp. 357–62. He compared the leaf structure of D. gyrans with other members of the genus in Movement in plants, pp. 362–4, arguing that the lateral leaflets in D. gyrans were rudimentary, at least in function. The lateral leaflets are noted for their rapid movements.
3
CD did not discuss Desmodium gyroides (now Codariocalyx gyroides) in Movement in plants. There is an annotated copy of Ernst Gottlieb Steudel’s Nomenclator botanicus (Steudel 1841) in the Darwin Library–CUL (see Marginalia 1: 788–9).
4
In his copy of Steudel 1841, 1: 493–6, CD marked, as well as Desmodium gyroides (see n. 3, above), D. adhaesivum, D. adscendens, Hedysarum uncinatum (a synonym of D. ancistrocarpum), D. polycarpum, D. prehensile, D. reptans, D. retinens, D. spirale, and D. uncinatum. Desmodium adhaesivum is now D. aparines; D. polycarpum is now D. heterocarpum; D. reptans is now D. axillare; D. spirale is now D. procumbens. None of them is a climber; none is discussed in Movement in plants. CD had discussed the gradation in the form of leaflets from leaf-climbers to tendril bearers in Climbing plants, p. 111.

Manuscript Alterations and Comments

3.2 like] ‘a’ del from ‘alike’
3.2 those of D. Gyrans] interl in CD’s hand

Please cite as “DCP-LETT-9106,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-9106