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Darwin Correspondence Project

From J. D. Hooker   [14 March 1858]1



My dear Darwin

Ledebour shall go tomorrow you are most welcome to it whenever you want it always.2 I quite see in what respect local Floras are much the best suited to your purpose; or rather, how they would be so, if they were worked out upon the same principles as the general Floras, but the fact that they are not so, and that they are hotbeds of bad big genera, is a very serious objection to the use of them. I cannot so well see, & in plain truth I cannot at all appreciate your objections to such a monograph as that on Urticeæ.3 Are not the number of varieties registered by Weddell very many? From what I know of Urticeæ I think it would not be difficult so to alter Weddells genera & species as to suit your views—thus—by raising to species a few of the varieties in those genera with 6–7 species & several varieties—Parietaria for instance, which would thus come under the genera with more than 10 species, & materially alter the result.

I shall be however most curious to see the results of Benthams British Flora—4 He reduces the Rubi to 6 species, I think, (& about 11 varieties, I suppose) which gives you a small very variable genus, whilst Babington has 28 species or so, besides varieties5—so Callitriche, of which Babington has several species but which Bentham reduces to 1 with 2? varieties. You must however take care not to get entête with your results— I shall certainly go over the Tasmanian Flora for your sake, & see whether or no I should not have noticed varieties to many small genera, to make their species consistently worked with the big—.6 I am quite sure I should. The object of these books you must remember is not to tell every thing about a plant, and perhaps least of all to tell the amount of their variation, but to lead others to 1st its name 2 affinities, 3 distribution, 4 uses—& so on— As a rule the amount of variation is a speciality affecting the species differently in different localities, & is therefore only recorded when the omission of its record might lead to the non recognition of the plant by the character.—7 All plants are variable: see how the descriptions teem with “vel”, “aut”, “et”, &c

Again, in most synoptical works (Br. Prodr)8 the species of monotypic genera are not described at all—their general characters alone being appended to the generic description— but all the species must be described in a large genus, & the larger the genus the greater length required of description.

Again, a variety is often made to save the trouble of altering a borowed specific character. thus,—supposing in the VDL Flora9 I have but one species of Banksia which is also an australian one described (amongst 50 others) by Brown, & my specimens differ a little from Brown’s character it is perhaps better to mark that difference by making it a β, than to alter Browns character in that point, which would perhaps require my adding a lot more words & perhaps require a further alteration of the characters of many other species.

The long & short of the matter is, that Botanists do not attach that definite importance to varieties that you suppose, they do not treat large & small genera equally & similarly, & the sum of inequalities thus produced tends to make the species of small genera look more invariable than of big.

Again, much depends on the generic idea— Cruciferæ have their genera made on their pods to a great degree, & its species & varieties too are very much confined to the pod. Stature & size hairs & foliage are so awfully variable in that Order that no one notices them in many cases— Well, you make many a new genus out of one species of an old one in that order, not because the pod is very materially different from that of the others of the old genus, but because its small difference is constant. The said new genus is no natural genus at all, in any other respect, & its stature & foliage may be & indeed often are much more variable than those of its quondam congeners—but no notice is taken of these matters— it is not the object of descriptive Botany to do so, or at least of systematic works to record them.

Had I been doing the Flora Indica10 as I should have done with an eye to making it a descriptive book of variation, I should most certainly have added varieties to most of the small genera, thus in Naravelia α & β. Adonis α, β, γ. Callianthemum α, β. Ceratocephalus α, β, γ. δ. Caltha α, β, γ. δ Isopyrum α, β, γ. Aquilegia α–ω! to render them equivalent to the varieties in Clematis, & other big genera & confounded your statistics—

Just look & see how much more frequently we notice under the monotypic genera its variations & variability, than we do in the polytypic (excuse the coined phrase).

So my dear Darwin do not be in a hurry with your conclusions— I am quite sure that had monotypic genera or oligotypic been at all materially less variable than polytypic it would not have escaped the sagacity of men like Linnæus, Brown DC. or Bentham11—& that it would force itself on the attention of any cautious observer.

Ever yrs affectionately | Jos D Hooker

CD annotations

1.5 hotbeds … use of them.] underl pencil; scored pencil
crossed pencil
Top of first page: ‘March 14th.’ pencil


The date is given by CD’s annotation and by the relationship to the preceding letter.
Ledebour 1842–53, which CD had asked to borrow (see letter to J. D. Hooker, 10 [March 1858]).
Weddell 1856. See the postscript to the preceding letter.
Bentham 1858. The work was not published until early in July (Publishers’ Circular, 16 July 1858,p. 295), but CD evidently intended to use it in his calculations: Bentham’s name is included in CD’s list of results, but no data are given (Natural selection, pp. 149, 152).
Babington 1851.
Hooker 1855–60, which was issued in parts (Wiltshear 1913).
CD discussed Hooker’s point in Natural selection, p. 161.
Hooker refers to Robert Brown’s Prodromus (Brown 1810).
Van Diemen’s Land (Tasmania) Flora (Hooker 1855–60).
Hooker and Thomson 1855.
Linnæus (Carl von Linné), Robert Brown, Augustin Pyramus de Candolle, and George Bentham.


Summary of JDH’s objections to CD’s survey of floras and conclusion that large genera vary more than small.

Letter details

Letter no.
Joseph Dalton Hooker
Charles Robert Darwin
Sent from
Source of text
DAR 104: 182–5
Physical description
8pp †

Please cite as

Darwin Correspondence Project, “Letter no. 2240,” accessed on 19 June 2019,

Also published in The Correspondence of Charles Darwin, vol. 7