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Darwin Correspondence Project

To T. H. Farrer   4 July [1874]1

Down, | Beckenham, Kent.

July 4th

My dear Farrer

I have read with much interest your article.2 It certainly is a very curious case. The older I grow the more I become impressed with the endless & unfathomable fluctuations of structure.— I do not much like C. Emerus; if I understand rightly the bowing of the claw of the vexillum becomes the sole adaptation for getting honey on the outside of the flower.3 I wonder whether other Pap. flowers have an elongated claw. Hooker will be here next Saturday & I will ask him.4

The only case, at all analogous to yours, of which I can think is Marcgravia of S. America, which has its sepals or bracts (I forget which) modified into nectariferous tubes, so placed that the visitors brush against the stamens & stigmas.5 As I have often said, you were a born naturalist.—

Yours most sincerely | Ch. Darwin


The year is established by the reference to Farrer’s article (see n. 2, below).
Farrer’s article, ‘Fertilisation of papilionaceous flowers—Coronilla’ (Farrer 1874), appeared in Nature, 2 July 1874.
In Farrer 1874, p. 169, Farrer had described and illustrated how the claw or base of the vexillum (the large central petal of a papilionaceous flower) in Coronilla emerus (now Hippocrepis emerus, scorpion senna) was elongated and straight with the upper part of the petal curved inward towards the base.
Joseph Dalton Hooker visited CD on Saturday 11 July 1874 (Emma Darwin’s diary (DAR 242)).
Flowers in many species of the tropical genus Marcgravia have modified bracteoles that act like nectaries.


Farrer, Thomas Henry. 1874. Fertilisation of papilionaceous flowers—Coronilla. Nature, 2 July 1874, pp. 169–70.


Has read THF’s article on Coronilla [see 9400] – "a very curious case"; is troubled by C. emerus.

Letter details

Letter no.
Charles Robert Darwin
Thomas Henry Farrer, 1st baronet and 1st Baron Farrer
Sent from
Source of text
Linnean Society of London (LS Ms 299/23)
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 9531,” accessed on 5 December 2022,

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