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Darwin Correspondence Project

To J. D. Hooker   [April 1852]1

(1) Prevalence of genera2 varying in one quarter of world & not in another, as in Rubus in Europe & Himm:—or varying universally as in Senecio.

Does3 any individual species keep pretty constant in one quarter & vary in another quarter? or vary in one particular way in one region, & differently in another?

2. Do the local or widely distributed species vary most?4

3. When an organ or part varies to a quite remarkable degree in the different species of a genus, does it not vary in some degree within the limits of the same species?5 Thus the position of the radicle6 said to vary in Guttiferæ, hence I believe would vary slightly in some of the individual species. So position of the embryo in Helianthemum.7

(4) I shd be extremely glad to hear of any remarkable cases of variation in important organs within same species, in such rare cases as occurs.—8

(5) When an organ is developed in an extraordinaryly great degree it is (according to Waterhouse)9 apt to be variable in same species; so it is, when developed in an extraordinarily little degree (ie when rudimentary). Is this likewise case when organ developed in some very unusual manner?—10

(6) If a list of highly variable plants were made out, would they not usually be members of genera having many species?11

6. Cases of plants which must for ever self-fecundate themselves;12 do such occur? as in plants always fecundated in bud.—13


The recipient and date are inferred from a draft of these queries headed: ‘Ap 1852 Questions for Hooker’ in DAR 206 (Letters). The list of questions has a few answers pencilled on it in Hooker’s hand (see nn. 5, 8, and 10, below). Later notes have been added to the manuscript by CD (see nn. 2, 3, and 4, below). The draft also carries additional notes made by CD.
CD made further notes on the manuscript after it was returned to him by Hooker. Above question (1) he added: ‘N.B. Look over Lindley Veg. K. & then ask Questions’. He refers to Lindley 1853, a copy of which is in the Darwin Library–CUL. See letter to J. D. Hooker, 15 November [1854].
CD subsequently added ‘(2)’ in pencil and marked the paragraph with a pencil cross.
CD added in ink: ‘see N. Zealand Flora. Introduction’. He refers to J. D. Hooker 1853–5, 1: xxxvi–xxxix.
Hooker added in pencil: ‘Aquilegia spurs—nectaries of Ranunculus not necessary’. Over this, CD has written in ink: ‘yes in Aquilegia, spurs of & in Nectaries of Ranunculus not necessary; then stamens in Clematis variable but constant in the species’. CD also added in pencil ‘(?)’.
CD subsequently underlined ‘radicle’ in ink and added: ‘Miers thinks plumule’. He refers to John Miers’s paper on the embryo and seed of the family Clusiaceae, also known as the Guttiferae (Miers 1855).
Beside this question CD subsequently wrote in pencil: ‘Lindley’s Elements of Plants would be best for picking out remarkable points of Structure’. He refers to Lindley 1841.
Hooker added in pencil: ‘Stamens most constant organs’.
Waterhouse 1846–8, 2: 452 n. 1, in which George Robert Waterhouse stated: As a general rule, where any species is characterized by a maximum of development of certain parts, those parts are more subject to variation in the different individuals of the species than are parts which approach more nearly to the normal conditions. CD later asked the same question in letters to H. C. Watson (see letter from H. C. Watson, 23 August 1855, n. 4) and Asa Gray (see letter to Asa Gray, 24 August [1855]). The passage is marked in CD’s copy of Waterhouse 1846–8, now in the Darwin Library–CUL.
Hooker added in pencil: ‘Nepenthes’. To this, CD added in pencil: ‘& Acacia— Sarracenia— Stigma of d[itt]o—’. The whole passage has been crossed through with pencil. CD later discussed this issue in Natural selection, p. 375.
Hooker added in pencil: ‘Yes because people have made most species of such’. To this, CD added in pencil: ‘Steudels Nomenclatur could count the Genera as in Salix—’. CD refers to Steudel 1840–1. See letters from J. D. Hooker, [3 November 1854] and [15 November 1854] for CD’s further examination of this question.
Hooker added in pencil: ‘Limosella Stratiotes many water plants’. CD wrote the names again in ink over Hooker’s note. These species of water plants and their self-fecundation are discussed in Natural selection, p. 63.
Hooker added some arithmetical calculations in the margin of the final paragraph in ink, and wrote, also in ink, ‘Berberis Darwinii’. This plant had been named by Hooker from specimens collected by CD on the Beagle voyage (see Correspondence vol. 2, letter from J. D. Hooker, [12 December 1843 – 11 January 1844], n. 8). The pollination mechanism in Berberis was of interest to CD (see Natural selection, p. 54) because many botanists believed it was self-pollinated whereas CD, following Joseph Gottlieb Kölreuter’s views, thought that cross-pollination was brought about by the activity of insects.


Questions on variation in nature: taxa varying in one region but not another. Variation between vs within species. Rarity of variation in important organs within a species. G. R. Waterhouse’s views on variation in highly developed organs, which CD relates to variation in rudimentary organs.

Asks for cases of obligate self-fertilising plants.

[CD annotation proposes using the Steudel Nomenclator botanicus (1821–4) to determine if variable species occur in genera with many species.]

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 107: 66–7
Physical description
Amem 3pp & Adraft 4pp †, †(by CD)

Please cite as

Darwin Correspondence Project, “Letter no. 1496,” accessed on 25 April 2019,

Also published in The Correspondence of Charles Darwin, vol. 5