# From Hubert Airy   7 December 1873

Edensor. | Kidbrook Grove. | Blackheath, London S.E.

7. December 1873.

My dear Sir

It is not easy to reject the notion that ‘twist’ has played a part in the history of Leaf-arrangement,—after an examination of the different species of Gasteria, a South African genus which I first saw exhibited by Dr. Hooker at the soirée of the R.S. last spring, and which I have lately examined more carefully in the Cambridge Botanical Gardens.—1

Here is a figure of Gasteria subnigricans,2 as seen from above:—

—and here is a series of diagrams of the other species, similarly projected, numbers standing for leaves.3

G. $\left\{\begin{array}{c}\text{longifolia}\\ \text{conspurcata}\\ \text{sulcata}\\ \text{Boweiana}\\ \text{carinata}\\ \text{lingua}\\ \text{angustifolia}\\ \text{angustata}\end{array}\right\}$

G $\left\{\begin{array}{c}\text{angustifolia}\\ \text{angustata}\\ \text{pluripunctata}\end{array}\right\}$

G $\left\{\begin{array}{c}\text{subnigricans}\\ \text{undata}\\ \text{glabra}\end{array}\right\}$

G $\left\{\begin{array}{c}\text{glabra}\\ \text{spiralis}\\ \text{carinata}\end{array}\right\}$

G $\left\{\begin{array}{c}\text{pulchra}\\ \text{pulchella}\\ \text{vittata}\\ \text{distans}\end{array}\right\}$

(I ought to have begun by thanking you for your kind letter:4 but I wanted to make sure of Gasteria.—

Perhaps I ought to refrain from troubling you with this but I cannot help thinking that you will be interested with the plain evidence, without comment.)

You kindly offered to lend me the paper you mentioned opposing my views—5 I should be much obliged if you would kindly do so, and I would return it as soon as possible. At present I am inspecting vaccination in Herefordshire,6 but hope to get home about a week before Christmas.

Thank you for your hints about bud-dissection— I long for leisure to do that and more.

I am, my dear Sir, | Yours very sincerely | Hubert Airy

Charles Darwin Esq. M.A., F.R.S. | Down, Kent.

## Footnotes

For more on Airy’s theory of phyllotaxy, see the letter from Hubert Airy, 17 March 1873 and n. 2. Gasteria is a genus of succulent plants in the family Asparagaceae. The soirée of the Royal Society of London took place at Burlington House on 26 April 1873 (Nature, 24 April 1873, p. 490). Airy refers to Joseph Dalton Hooker.
Gasteria subnigricans is a synonym of G. brachyphylla var. brachyphylla.
Gasteria longifolia, G. conspurcata, and G. angustifolia (Aiton) Duval are synonyms of G. disticha var. disticha; G. sulcata, G. undata, and G. glabra are synonyms of G. carinata var. carinata. Gasteria lingua and G. spiralis are synonyms of G. obliqua; G. angustifolia Haw is a synonym of G. nigricans; G. pluripunctata is a synonym of G. acinacifolia; G. subnigricans is a synonym of G. brachyphylla var. brachyphylla. The names Gasteria boweiana, G. angustata, G. pulchella, G. vittata, and G. distans have never been in use.
CD’s letter has not been found.
CD sent 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; see Correspondence vol. 22, letter from Hubert Airy, 8 January 1874). CD’s copies of American Naturalist are in the collection of unbound journals in the Darwin Library–CUL. CD had already lent Airy a copy of Chauncey Wright’s paper on leaf arrangement (Wright 1871; see Correspondence vol. 20, letter from Hubert Airy, 31 May 1872).
Airy was medical inspector to the Local Government Board.

## Bibliography

Beal, William James. 1873. Phyllotaxis of cones. American Naturalist 7: 449–53.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

## Summary

Illustrates, with reference to different species of Gasteria, the role of twisting in the development of leaf arrangement.

## Letter details

Letter no.
DCP-LETT-9175
From
Hubert Airy
To
Charles Robert Darwin
Sent from
Blackheath
Source of text
DAR 159: 27
Physical description
4pp