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Darwin Correspondence Project

To W. T. Thiselton-Dyer   23 November [1880]1

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

Nov. 23d

My dear Dyer

Very many thanks for your most kind note, but you think too highly of our work, not but what this is very pleasant.—2

I am deeply interested about Welwitschia. When at work on the pegs or projections, I could not imagine how they were first developed before they could have been of mere mechanical use.3 Now it seems possible that a circle between radicle & hypocotyl may be permeable to fluids & thus have given rise to projections so as to expose larger surface. Could you test Welwitschia with permanganate of potassium, if like my “pegs” the lower surface wd be coloured brown like radicle & upper surface left white like hypocotyl.—4 If such an idea, as yours of absorbing organ had ever crossed my mind, I wd have tried my hypocotyls in weak C. of Ammonia to see if it penetrated on line of junction more easily than elsewhere.— I daresay projection in Abronia & Mirabilis may be an absorbant organ.5

It was very good fun bothering the seeds of Cucurbita by planting them edgeways, as would never naturally occur & then the peg could not act properly.6 Many of the Germans are very contemptuous about making out use of organs; but they may sneer the souls out of their bodies, & I for one shall think it the most interesting part of Natural History.

Indeed, you are greatly mistaken if you doubt for one moment on the very great value of your constant & most kind assistance to us.

I have not seen the pamphlet & shall be very glad to keep it.7 Frank,8 when he comes home will be much interested & pleased with your letter—.

Pray give my kindest remembrances to Mrs Dyer.9

Ever yours very sincerely | Ch. Darwin

This is very untidy note, but I am very tired with dissecting worms all day.—

Read last Chapter of our Book & then you will know whole contents.—

P.S. | When next you walk in garden look under any tree on bare ground or on poor turf of Robinia pseudo-acacia for me,—& see if worms have drawn the petioles of leaves into mouths of burrows.10


I want to know whether they uniformly or almost uniformly draw them in by basal, blunt end or by apex. I do not suppose that they are now at work, but by pulling up any old tuft you wd easily see which end of petiole was within mouth of burrow.—

My whole soul is absorbed with worms just at present!


The year is established by the reference to Movement in plants.
The letter from Thiselton-Dyer has not been found; it contained remarks on Movement in plants (see letter to W. E. Darwin, 23 [November 1880]).
In Movement in plants, pp. 102–6, CD had discussed the role of the heel or peg in opening the seed-coats in species of Cucurbitaceae and several other plants; Joseph Dalton Hooker had mentioned Thiselton-Dyer’s interest in this point (see letter from J. D. Hooker, 22 November 1880 and n. 5).
CD had applied permanganate of potassium to the petioles in Megarrhiza californica, and to the peg in Cucurbita ovifera, noting that these organs were stained brown like the radicle, suggesting that they acted functionally like a root (see Movement in plants, pp. 81, 102–4).
CD had described the heel at the base of the hypocotyl in Abronia umbellata (sand verbena) in Movement in plants, pp. 105–6; on a similar structure in Welwitschia mirabilis, see the letter from J. D. Hooker, 22 November 1880 and n. 5.
See Movement in plants, pp. 103–4.
Harriet Anne Thiselton-Dyer.
CD reported on the manner in which leaves of Robinia pseudoacacia (black locust or false acacia) were drawn into worm burrows in Earthworms, pp. 81–2.


Bower, Frederick Orpen. 1881. On the germination and histology of the seedling of Welwitschia mirabilis. Quarterly Journal of Microscopical Science n.s. 21: 15–30.

Movement in plants: The power of movement in plants. By Charles Darwin. Assisted by Francis Darwin. London: John Murray. 1880.


WTT-D’s suggestion about absorbent function of pegs in Abronia suggests origin of pegs in Welwitschia, which deeply interests CD. Previously could not see how pegs became large enough to be of mechanical use. Now thinks tissue between hypocotyl and radicle absorbs fluid, which would favour rise of peg to expose larger surface.

Rejects German contempt for investigating use of organs.

Asks WTT-D to observe how worms draw Robinia leaves into burrows.

Letter details

Letter no.
Charles Robert Darwin
William Turner Thiselton-Dyer
Sent from
Source of text
Royal Botanic Gardens, Kew (Darwin: Letters to Thiselton-Dyer, 1873–81: ff. 209–11)
Physical description
ALS 5pp

Please cite as

Darwin Correspondence Project, “Letter no. 12843,” accessed on 31 January 2023,