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Darwin Correspondence Project

From Hubert Airy   21 July 1872

13. Eliot Place. | Blackheath. S.E.

1872. July 21.

My dear Sir

I am afraid I made a bad mistake in my letter yesterday, in saying that the leaf belonging to the topmost node in grass-stems is obsolete. On examination I see that the leaf is fully developed; and I hope you will obliterate that passage from my letter.1

With this, I send one or two lilac twigs, which present a characteristic series of variations from the normal 2-whorl, in illustration of the ‘nodal’ question.2

I could also show you an oak-twig affecting a succession of 3-whorls with long internodes from whorl to whorl; as a specimen of variation from the alternate towards the verticillate arrangement.3

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


In Airy 1874, pp. 304, Airy discussed variability of the number of leaf-ranks in the same species, giving as an example whorls of three being produced by plants like lilacs that usually bear whorls of two. The ‘nodal’ question relates to Airy’s view that the node had no independent importance and existed only as the starting point of the leaves (see letter from Hubert Airy, 20 July 1872 and n. 1).
The variation in oak showing the alternate going to a verticillate (or whorled) arrangement involved an increase from one leaf per node to three per node.


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.


Corrects a factual error in his previous letter [8418].

Sends specimens illustrative of the "nodal" question.

Letter details

Letter no.
Hubert Airy
Charles Robert Darwin
Sent from
Source of text
DAR 159: 19
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 8422,” accessed on 29 September 2020,

Also published in The Correspondence of Charles Darwin, vol. 20