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# From Hubert Airy   13 March 1874

Barrow House. | Keswick. | Cumberland.

13th. March. 1874.

My dear Sir

I have re-written my paper on Leaf-arrangement, embodying the views contained in my last two letters to you; and I propose to send it to the Royal Society, in spite of the unfavourable criticism which the former paper met with from the R.S. referees.1

May I beg the favour of a line from you to say if you will be kind enough to “communicate” my new paper to the Society—?—though I am almost ashamed of asking you to stand godfather to something that may be doomed to suffocation.2 If the R.S. decline to print it, I shall certainly get it published in some journal (probably Nature), for I am sure it has a grain or two of truth in it which may thrive on wider criticism. I think I have found a new principle which has played an important part in the history of leaf-arrangement,— I mean spontaneous variability in the number of vertical leaf-ranks.3

The variations which present themselves at the present day are such as (I believe) cannot be explained on any other hypothesis. Let me mention a single example— I have found three ash-shoots, all rising from the same stump, the first exhibiting perfect crucial order (whorls of 2, the normal leaf-order of ash), the second exhibiting perfect alternate ($\frac{2}{5}$) order, and the third exhibiting perfect whorls of 3.

I cannot see how any one of these three arrangements could have been modified by slow degrees into any other of the three; but if by a sheer stroke of variation the old stump produced buds with 5 and 6 vertical ranks as well as buds with 4, I can see that, while 4 ranks would almost necessarily be packed into crucial order, 5 would almost necessarily be packed into alternate order $\frac{2}{5}$, and 6 into whorled order with whorls of 3.— And I suppose there may have been similar strokes of favourable variation in former days.

On many of the forms so produced, I suppose vertical condensation to have operated.4

Can you tell me if there is variability in the number of rays of any species of Star-fish?— Different species, I believe, have different numbers of rays; and that difference of number could only have been produced (I suppose) by strokes of variation.5

If such be the case, it furnishes a striking analogy to what I suppose to take place in the vegetable kingdom.

An echinus and an echinocactus6 might fairly share alike in the operation of so general a cause as that (supposed) of variation of number of vertical (or radial) ranks.

The two points on which I am troubling you are

1. ? Communication of paper to R.S.

2. ? Variability of rays of star-fishes.

Believe me, my dear Sir, | Yours very sincerely, Hubert Airy

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

## Footnotes

Airy’s previous two extant letters to CD are Correspondence vol. 21, letter from Hubert Airy, 7 December 1873, and this volume, letter from Hubert Airy, 8 January 1874. Airy’s earlier paper had been rejected for publication in the Transactions of the Royal Society of London (see Correspondence vol. 21, letter from Hubert Airy, 26 [September–November 1873]), but an abstract had been published (H. Airy 1873).
CD did communicate Airy’s revised paper to the Royal Society. It was read at a meeting of the society in April 1874, but only an abstract of the paper was published in the Proceedings of the Royal Society of London (H. Airy 1874). The summary of Airy’s argument (H. Airy 1874, p. 307) was reprinted in Nature, 14 May 1874, pp. 36–7.
See H. Airy 1874, pp. 304–5.
See H. Airy 1874, pp. 305–7.
Starfish typically have five rays or arms, but some always have more and others, such as species in the genus Solaster have a variable number of rays (see E. Forbes 1841, pp. 109–15).
Echinus is a genus of sea urchins; Echinocactus is a species of spiny cactus.

## Bibliography

Airy, Hubert. 1873. On leaf-arrangement. Abstract. Communicated by Charles Darwin. [Read 27 February 1873.] Proceedings of the Royal Society of London 21 (1872–3): 176–9.

Airy, Hubert. 1874. On leaf-arrangement. Abstract. Communicated by Charles Darwin. [Read 30 April 1874.] Proceedings of the Royal Society of London 22 (1873–4): 298–307.

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

Forbes, Edward. 1841. A history of British starfishes, and other animals of the class Echinodermata. London: John van Voorst.

## Summary

Has rewritten paper on leaf arrangement after criticism by Royal Society referees. Has found new factor influencing leaf arrangement, i.e., spontaneous variability in the number of vertical leaf-ranks.

## Letter details

Letter no.
DCP-LETT-9357
From
Hubert Airy
To
Charles Robert Darwin
Sent from
Keswick
Source of text
DAR 159: 29
Physical description
6pp

## Please cite as

Darwin Correspondence Project, “Letter no. 9357,” accessed on 20 October 2019, https://www.darwinproject.ac.uk/letter/DCP-LETT-9357.xml

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

letter