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Darwin Correspondence Project

From J. H. Gilbert   31 December 1875

Harpenden St. Albans

Decr 31, 1875

Dear Sir,

I am truly sorry to have allowed your two kind letters to remain so long unacknowledged. The first came (with the Tables returned), when I was with a yachting party north of Scotland, & the second when I was much occupied after my return home.1 I have since waited to say something of our further observations about Fairy-rings.2 Late in the Autumn Mr. Lawes found on igniting some soil apparently covered with mycelium that it remained white after ignition.3 Following this up in the Laboratory we found that much at any rate of the white matter was incombustible; and qualitative chemical examination of the residue showed it to contain much carbonate of lime, and only traces of phosphoric acid, whilst the examination of the ash of some fungi (a. nudus) showed much phosphoric acid, and much potass, but scarcely traces of lime, thus confirming previous analyses of the ash of various fungi.4 It would thus appear that the white matter coating the soil at that date was exhausted mycelium? This is obviously an interesting point, and calls for further experiment at other periods of the year.

With regard to the fungi not reappearing where they have grown before in the case of fairy rings, may it not be a question how far this may be due to the exhaustion of the materials for growth by the fungi themselves or how far by the luxuriant growth of the grasses which succeed them—adding perhaps the force of competition to exhaustion? On this point I may mention that a friend assures me that in the case of a “ring” yielding edible fungi which are always gathered (and so do not manure the grasses)5 the crop reappears on the same and not on an annually extending ring. I may add that this autumn large specimens of Agaricus arvensis appeared in more or less complete rings on one of our highly manured plots where individual specimens had previously been observed.6 Otherwise the prominent development of rings is, as stated in the “Note,” on the plots exhausted of potass and of nitrogen in such condition as to be available to the other plants. There is obviously much left to learn before we know all about this curious subject; & I am extremely glad to hear that you are making observations upon it.

Pray accept my best thanks, better late than never, for your kind offer to send me a copy of your book on “Insectivorous plants”.7 I need hardly say I shall be proud to receive one from you. I was much interested to hear some notices of your observations on the subject given by Professor Dyer at meetings of the Scientific Committee of the Hort. Soc.;8 and I remember the question occurred to me at the time, whether the plants appropriated the animal matter directly, or only its products of decomposition. I am not aware of your evidence and arguments on this point; but the interesting facts you were good enough to communicate in your last letter, as to the remarkable rapidity with which phosphate & carbonate of ammonia are absorbed and affect the contents of the cells, are at any rate consistent with the supposition that it is the products of decomposition rather than the animal matters as such that serve as food to the plants?

I was much gratified, as also was my brother, the Editor of the Memoir, to hear that you had been interested in the Memorials of our dear Mother.9

With the best wishes of the season, | I am, Dear Sir | Your’s sincerely | J. H. Gilbert

Charles Darwin Esqre., &c. &c. &c.


Gilbert had sent CD tables giving the full results of experiments carried out at the agricultural station at Rothamsted on the effects of different manures on permanent meadow land (see letter from J. H. Gilbert, 24 July 1875 and n. 4). CD returned the tables with his letter to J. H. Gilbert, 11 August 1875; his second letter has not been found.
Gilbert had presented a paper on 3 June 1875 on fairy-rings (fungi that grow in circles) at the Linnean Society (‘Note on the occurrence of “fairy-rings”’; J. H. Gilbert 1875). For CD’s interest in fairy-rings, see the letter from James Paget, 7 July 1875, the letter from M. J. Berkeley, 13 July 1875, and the letter to J. S. Burdon-Sanderson, 16 July 1875.
Gilbert collaborated with John Bennet Lawes at the agricultural research station at Rothamsted. Mycelium is the vegetative part of a fungus, and is a mass of branching filaments.
See J. H. Gilbert 1875, p. 20. ‘a. nudus’: Agaricus nudus, a synonym of Lepista nuda, the wood blewit or blue stalk mushroom.
Gilbert suggested that decaying fungi provided a rich nitrogenous manure to the adjacent vegetation, and thus gave rise to patches of dark green luxuriant grass far superior to the surrounding grass (J. H. Gilbert 1875, p. 22).
Agaricus arvensis, the horse mushroom, sometimes forms fairy-rings and likes rich soils.
Insectivorous plants had been published on 2 July 1875 (CD’s ‘Journal’ (Appendix II)).
The Scientific Committee was one of the committees of the Royal Horticultural Society of London; the others were the Floral and the Fruit committees. William Turner Thiselton-Dyer had communicated CD’s work on Pinguicula (butterwort) to the Scientific Committee of the society on 1 July 1874 (see Correspondence vol. 22, letter to W. T. Thiselton-Dyer, 28 [June 1874] and n. 4).
See letter to J. H. Gilbert, 11 August 1875 and n. 3. Josiah Gilbert had edited Autobiography and other memorials of Mrs. Gilbert (A. Gilbert 1874). The Gilbert brothers’ mother, Ann Gilbert, was a children’s writer and poet.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Gilbert, Ann. 1874. Autobiography and other memorials of Mrs Gilbert, (formerly Ann Taylor). Edited by Josiah Gilbert. 2 vols. London: C. Kegan Paul & Co.

Gilbert, Joseph Henry. 1875. Note on the occurrence of ‘fairy-rings’. [Read 3 June 1875.] Journal of the Linnean Society (Botany) 15 (1877): 17–24.

Insectivorous plants. By Charles Darwin. London: John Murray. 1875.


Discusses fairy rings.

Letter details

Letter no.
Joseph Henry Gilbert
Charles Robert Darwin
Sent from
Source of text
Rothamsted Research (GIL13)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 10331F,” accessed on 20 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 23