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Darwin Correspondence Project

From Hubert Airy   8 January 1874

Edensor. Kidbrook Grove. | Blackheath S.E.

8 Jany. 1874.

My dear Sir

Herewith I return the “American Naturalist” which you kindly lent me, with apologies for detaining it so long.

Professor Beal’s paper is very interesting.1 The varieties of leaf-order, which he has found in cones from the same tree or from different trees of the same species,2 do not surprise me, because I have found some thing of the same kind in other plants: for instance, out of 100 dandelion heads I found 4 or 5 with 10 and 16 spirals (instead of the normal 13 and 21).

Prof. Beal’s paper shows (what I had already found for myself) the incompleteness of my former theory, but it does not invalidate the soundness of the principles that I have sought to lay down, nor the correctness of my theory as applied to a wide range of instances.3

With best wishes for the New Year, | Believe me yours very sincerely | Hubert Airy

Charles Darwin Esq. M.A., F.R.S..


CD had lent Airy the August 1873 issue of American Naturalist; it contained William James Beal’s ‘Phyllotaxis of cones’, in which Beal disagreed with Airy’s view that certain fractions expressing angular divergence were necessarily excluded by the geometry of the case (Beal 1873, p. 451).
For Beal’s observations on varieties of spiral patterns in cones from five different tree species, see Beal 1873, pp. 451–2.
Airy’s theory of phyllotaxis (leaf arrangement) was published in H. Airy 1873; he corrected and extended his theory in H. Airy 1874.


W. J. Beal’s paper ["Phyllotaxis of cones", Am. Nat. 7 (1873): 449–53] shows incompleteness of HA’s theory, but does not invalidate his basic principles on origin of leaf arrangement or the broad applicability of the theory.

Letter details

Letter no.
Hubert Airy
Charles Robert Darwin
Sent from
Source of text
DAR 159: 28
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9232,” accessed on 19 March 2019,

Also published in The Correspondence of Charles Darwin, vol. 22