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Darwin Correspondence Project

To J. D. Hooker   5 January [1873]1

Down, | Beckenham, Kent.

Jan. 5th

My dear Hooker

It is so stupid to publish well-known facts, that I shd. be greatly obliged if you would tell me, whether it is known that the glandular hairs of plants have the power of absorption, as well as of excretion.— I had better explain what I have seen. When minute doses of salts of ammonia & of other nitrogenous fluids are given to the glands of Drosera, besides the movement of the tentacles, another change ensues after a time, viz the cells of the glands, (& afterwards of the whole tentacle) which were before filled with limpid purple fluid undergo what I call segregation. That is, little masses of protoplasmic matter are formed, which float in colourless liquid, & undergo incessant changes of form, like Amœbæ. Now Carbonate of Ammonia is absorbed with extraordinary rapidity & causes segregation sometimes in a few seconds or at most in a few minutes. I thought, therefore, that a weak solution of the the Carbonate of A. would be good to test glandular hairs; & I find that the hairs of 2 species of Saxifrage, of Primula sinensis, & of Pelargonium zonale (though the globular heads of the hairs of the latter do not excrete, as far as I can see) all undergo segregation, showing that the Carbonate has been absorbed. With the Pelargonium absorption was evident in 3 minutes. As rain-water contains salts of Ammonia, & as the glandular hairs are infinitely numerous in some cases, as on the Primula, their power of absorption can hardly be quite indifferent in the nutrition of the plant.2

I find roots of some very few plants, which I have tried, also absorb the Carbonate; & it was truly wonderful to see how rapidly the segregating process ran up the cells of the roots.—

There is one other thing I want to bother you about. How are you off for plants of Drosophyllum?3 Could you lend me one?

Now that I have written out my notes I find several points which I ought to have observed in this most perplexing plant. But if you think your plants wd be sure to survive till the summer, they wd then be in a better state for observation.

Have you read Galton’s Essay in Fraser? The idea of castes forming spontaneously & the members inter marrying seems quite new; but the more I think of the subject the less possible does it appear to me that the plan could ever be carried out.4

I shd also much like to hear, but only if you have leisure, what you think of Greg’s enigmas.5 It seems to me grand poetry; but he is too Utopian & too full of faith for me to sympathise thoroughly with him. Altogether I have been rather disappointed in the book. I shd think he must be a delightful man.

Whenever you write do tell me whether Ayrton has given you any more trouble.6 I was glad to see the little notice in Nature about you & the Belgian Academy.7

Ever yours affectionately | Ch. Darwin

Wd. you mention the absorption of C. of Ammonia by the glandular hair to Oliver8 who is so brim-full of knowledge, & ask him.— Or any one else at Kew.—

I have also been wonderfully interested in Decandolle’s “Hist. des Sciences”,—excepting the part about Man, which seems to me rather poor.—9 This book exalts D.C. higher than ever in my estimation.—


The year is established by the relationship between this letter and the letter from J. D. Hooker, 7 January 1873.
CD published his observations in Insectivorous plants, pp. 344–55. Drosera is the genus of sundews. The two saxifrages were Saxifraga umbrosa (Pyrenean saxifrage) and S. rotundifolia (round-leaved saxifrage). Primula sinensis is the Chinese primrose. Pelargonium zonale is the horseshoe geranium. CD used the term ‘aggregation’ rather than ‘segregation’ in his published work (see ibid., p. 17).
CD wanted a specimen of Drosophyllum lusitanicum (Portuguese sundew; Drosophyllum is a monospecific genus) for his work on insectivorous plants (see also Correspondence vol. 17).
Galton’s paper, ‘Hereditary improvement’ (Galton 1873a) was published in Fraser’s Magazine (see also letter to Francis Galton, 4 January [1873] and n. 3).
William Rathbone Greg’s Enigmas of life (Greg 1872).
Hooker had been in dispute with the first commissioner of works, Acton Smee Ayrton, over the running of the Royal Botanic Gardens, Kew, since before 1871. On Hooker’s dispute with Ayrton, see Nature, 11 July 1872, pp. 211–16; L. Huxley ed. 1918, 2: 159–77; Macleod 1974; Port 1984; Drayton 2000, pp. 211–20, Endersby 2008, pp. 282–300; and Correspondence vols. 19 and 20.
Nature, 2 January 1873, p. 168, recorded that the Académie royale de Belgique had elected Hooker an associate member ‘as their contribution to the Kew controversies’ (see n. 6, above).
Daniel Oliver.
CD’s annotated copy of Candolle 1873 is in the Darwin Library–CUL; he had received it from Alphonse de Candolle in 1872 (see Correspondence vol. 20, letter to Alphonse de Candolle, 2 November [1872]). CD probably refers in particular to the chapter headed ‘Sur la part d’influence de l’hérédité, la variabilité et la sélection dans le développement de l’espèce humaine et avenir de cette espèce’ (On the influence of heredity, variability, and selection on the development of the human species and the future of this species).


Asks whether his observations on absorptive powers of glandular hairs of plants are new facts.

Asks for a Drosophyllum.

Comments on Francis Galton’s article in Fraser’s Magazine,

Greg’s Enigmas,

and Alphonse de Candolle’s Histoire des sciences.

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 94: 243–7
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 8726,” accessed on 20 June 2018,

Also published in The Correspondence of Charles Darwin, vol. 21