From George Henslow   13 April 1868

St Johns Parsonage | St Johns Wood

13/4/68

Dear Mr Darwin,

I have delayed writing, in order to have an opportunity of reading M. De Candolle’s paper for which let me give you very many thanks, & which I hope to return carefully in a short time.1 He has proved algebraically from assumed mathematical principles, analogous to the arrangt of leaves in nature, that the series of fractions are really convergents of a continued fraction,—as long since stated. (as M. Decandolle says, but not proved,) by Messrs Schimper & Braun 1838.2 This nothing whatever to do with my investigations though it is a corroboration of certain parts.

Please to thank Mrs (?) Darwin for kindly writing about the lectures in the N. of England. I have written to Miss Clough & offered my services; as I shall be very happy to give a course of lectures as proposed.3

With kind regards believe me | yrs very truly | Geo: Henslow

1
Henslow refers to Casimir de Candolle’s paper ‘Théorie de l’angle unique en phyllotaxie’ (C. de Candolle 1865). CD’s presentation copy of an offprint of the article is in the Darwin Pamphlet Collection–CUL. For CD’s own work on phyllotaxy, see Correspondence vol. 11. CD’s phyllotaxy notes are in DAR 51: 6–32; there are also notes by George Howard Darwin in DAR 192: 1–7.
2
Henslow refers to Karl Friedrich Schimper and Alexander Carl Heinrich Braun, both of whom published works on the doctrine of phyllotaxy between 1830 and 1835 (DSB). Neither published on the subject in 1838, but Henslow may have misunderstood a remark by Candolle that refers to work done in 1838 by Auguste Bravais and Charles Frédéric Martins contradicting Braun and Schimper’s view that the angular distance separating leaves in a spiral arrangement differed from species to species and even in different parts of the same plant (C. de Candolle 1865, p. 199). The paper Candolle alludes to, published in 1837, was ‘Résumé des travaux de MM. Schimper et Braun sur la disposition spirale des organes appendiculaires’ (Martins and Bravais 1837). Candolle supported the views of Martins and Bravais, and his paper offered a proof of the ‘unique angle’ theory.
3
No letter from Emma Darwin mentioning lectures has been found. Henslow probably refers to Anne Jemima Clough, who was a founder member of the North of England Council for Promoting the Higher Education of Women. The Council commissioned lectures by distinguished visitors (Clough 1897, pp. 121–4).

Please cite as “DCP-LETT-6115,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-6115