Ɛpsilon

To Francis Darwin   13 [September 1878]1

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

13th

My dear F.

Glass Tubes come & I think will do very well.—2

Will you ask at Kew to look at soon any plants of Oxalis carnosa, for chance of old flower-peduncles being still on. With upright main flower-peduncle (see fig. 2. in diagram), the sub-peduncles bearing young pods assume the position there shown,. (Afterwards they bend up to scatter seed).— Now if main flower peduncle were placed horizontally would sub-peduncles assume position of (3) or (4)? Perhaps there may be a naturally somewhat inclined old flower-peduncle, which would partially answer this question, which is important for me, as it would show whether movement of sub-peduncle is governed by geotropism or epinasty.— I stupidly did not ascertain this, though I made many tracings of movements of sub-peduncles.3

Also keep your eyes open for any plant not a climber in pot with tip of shoot bowed downwards or hooked, or even forming a rectangle.— I am much perplexed about this, & when you come back, I must get you to read up De Vries on Epinasty. With Smithia Pfundii, which always has end of shoot forming a rectangle, this position seems governed by geotropism, (& not as I had supposed by epinasty) & so I believe it is with Ampelopsis.— Some growing lilies, if my memory is right, grow with tips hooked.— I know Epipactis does so.— I want much to trace an Epinastic or Hyponastic movement—4

If you could find any one or two such plants at Kew, I could probably borrow them.

Have you any Tracing paper up stairs????— I am running rather short— I am working at Heliotropism, with subdued light, & at ApoGeotropism.5

Yours affect | C. Darwin

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1
The month and year are established by the relationship between this letter and the letter to Francis Darwin, 12 September [1878].
3
CD later concluded that the movement of the peduncle after the flower withered was due to epinasty (the downward movement of an organ due to greater longitudinal growth on its upper side); see Movement in plants, pp. 503–6. Oxalis carnosa is a synonym of O. magellanica, fleshy sorrel. One of the tracings is in DAR 209.11: 73 (see Movement in plants, p. 505).
4
Hugo de Vries discussed hyponasty (the upward movement of an organ due to great longitudinal growth on its lower side) and epinasty in Vries 1872, p. 252. See also letter from Francis Darwin, [21 July 1878] and n. 6, and Movement in plants, pp. 267–8. Smithia pfundii is a synonym of Aeschynomene pfundii. See Movement in plants, pp. 274–6. CD discussed the movements of Ampelopsis tricuspidata (a synonym of Parthenocissus tricuspidata, Boston ivy) in Movement in plants, pp. 272–5. Epipactis is helleborine; CD did not discuss it in Movement in plants, but he had described two species in the genus in Orchids 2d ed., pp. 93–103.
5
CD described the effects of low light-levels on plants in Movement in plants, pp. 420–32, and apogeotropism (bending against the direction of gravity) throughout.

Manuscript Alterations and Comments

2.1 soon] interl
2.2 With] altered from ‘with’
2.3 there shown,] interl
2.4 main] after del illeg
2.6 partially] interl
3.1 not a climber] interl
3.8 or Hyponastic] interl
4.1 one or two] interl
4.2 them.] after del ‘it’
5.1 rather] interl
5.2 am] above del illeg
5.2 ApoGeotropism] ‘Apo’ interl
6.1 Yours] after del ‘under simi’
Diagram 1: scribbled over red crayon
8.1 Flower] after del ‘Plant’

Please cite as “DCP-LETT-11692,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11692