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Darwin Correspondence Project

To John Scott   2 July [1863]1

Down Bromley Kent

July 2d

Dear Sir

Many thanks for capsules.—2 I would give table of Auricula, especially owing to enclosed extract which you can quote.3 Your facts about varying fertility of the Primulas will be appreciated by but very few Botanists, but I feel sure that the day will come when they will be valued.—

By no means modify even in slightest degree any result.—4 Accuracy is the soul of Natural History. It is hard to become accurate; he who modifies a hair’s breadth will never be accurate. It is a golden rule, which I try to follow, to put every fact which is opposed to one’s preconceived opinion in the strongest light.— Absolute accuracy is the hardest merit to attain & the highest merit.— Any deviation is ruin—

Sincere thanks for all your laborious trials on Passiflora.5 I am very busy & have got two of my sons ill; I very much fear with scarlet-fever;6 if so, no more work for me for some days or weeks.— I feel greatest interest about your Primula cases. I think it much better to count seed than to weigh; I wish I had never weighed: counting is more accurate, though so troublesome.—

Yours sincerely | C. Darwin

[Enclosure 1]7

Prof. Treviranus says (Botanische Zeitung 1863 p. 4.) that according to Koch & Tausch all species of Primula, present two forms, except P. longiflora which is always short-styled.8

Prof. T. (idem p. 6.) seems to suspect that the long-styled P. auricula is sterile; for he says he found a plant of this long-styled form growing near a short-styled form, & the numerous flowers had not produced a single seed-capsule.

[Enclosure 2]9


“Various authors have remarked that the Hottonia palustris presents two forms. Fresh Specimens sent to me from N. Wales were grandly dimorphic.10 In the long-styled form, the pistil is more than twice as long as in the other form, & projects far out of the flower; the stigma is smaller & rougher than that of the short-styled: the anthers lie within the tube of the corolla. In the short-styled form, the anthers project far out of the flower & correspond in height with the projecting stigma of the other form; as does the short pistil with the short stamens of the long-styled form.— But the most remarkable difference is in the size of the pollen-grains: those from the short-styled flowers, when distended with water, are 14/14,000 of an inch in diameter; those from the long-styled (& therefore from the shorter stamens) are 9/14,000 in diameter. Spheres differing in the proportion of 14 to 9 in diameter presented under the microscope a most remarkable contrast. The contents of the larger pollen-grains certainly seemed to be coarser-grained & of a browner colour.11


The year is established by the reference to Scott 1864a, which was written in 1863 and read before the Linnean Society on 4 February 1864. See letter from John Scott, [3 June 1863].
The seed capsules referred to were apparently sent in a letter to CD which has not been found (see n. 3, below). The specimens have not been identified, but probably resulted from Scott’s experiments on either Primulaceae or orchids.
See enclosure 1 and n. 7, below. In a letter which has not been found, Scott had apparently asked CD whether he should give the results from his crossing experiments with the two forms of Primula auricula. In Scott 1864a, pp. 86–90, Scott tabulated his results from homomorphic and heteromorphic crosses with P. auricula. He noted that, since CD had published evidence of the functional dimorphism of this species (‘Dimorphic condition in Primula), he had no intention of giving the results from these crosses in detail. He continued (Scott 1864a, pp. 86–7): My attention, however, has been lately directed to a tacit implication of the absolute sterility of the long-styled form. As this view is certainly erroneous, I will give, for the satisfaction of those who have had no means of testing the point at issue, the results of my own experience. Scott’s reference is to Treviranus 1863a, p. 6; see Scott 1864a, p. 90.
Some indication of the nature of Scott’s statement in the missing letter is given by Scott’s letter to CD of 23 July [1863].
Scott’s letter has not been found, but see the letter to John Scott, 6 June [1863] and n. 11.
Emma Darwin recorded in her diary (DAR 242) on 2 July 1863: ‘boys with sore throat’. The reference may be to George Howard, Francis, or Horace Darwin; Leonard Darwin had contracted scarlet fever in 1862 (see Correspondence vol. 10).
Enclosure 1 has been attached to this letter on the basis of Scott’s reply, which establishes that CD sent notes on Treviranus 1863a with this letter (see letter from John Scott, 23 July [1863]).
The references are to Treviranus 1863a, p. 4, Koch 1843–4, 2: 673, and Tausch 1821, p. 355. There is an annotated copy of Treviranus 1863a in the Darwin Pamphlet Collection–CUL. Primula longiflora is a synonym of P. halleri.
In his letter to Scott of 20 [June 1863], CD had offered to send Scott his observations on heterostyly in Hottonia palustris. See also Scott’s letter to CD of 23 July [1863], which confirms that CD’s notes were sent with this letter. Scott quoted this memorandum in Scott 1864a, pp. 78–9.
The specimens of Hottonia palustris referred to were sent to CD from Llandudno, Carnarvonshire, by his niece Margaret Susan Wedgwood (see Correspondence vol. 10, letters from M. S. Wedgwood, [before 4 August 1862] and [6 August 1862], and letter to K. E. S., L. C., and M. S. Wedgwood, 4 [August 1862]). CD’s original notes on the specimens are in DAR 110: A16.
CD reported this observation in Forms of flowers, p. 51.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

‘Dimorphic condition in Primula’: On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations. By Charles Darwin. [Read 21 November 1861.] Journal of the Proceedings of the Linnean Society (Botany) 6 (1862): 77–96. [Collected papers 2: 45–63.]

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

Koch, Wilhelm Daniel Joseph. 1843–4. Synopsis florae Germanicae et Helveticae, exhibens stirpes phanerogamas rite cognitas, praemissa generum dispositione secundum classes et ordines systematis Linnaeani conscripta. 2d edition. 2 vols. Frankfurt: Fridericus Wilmans. Leipzig: Gebhardt & Reisland.

Tausch, Ignaz Friedrich. 1821. Beobachtungen über das Längenverhältniss der Befruchtungsorgane bei der Gattung Primula. Flora (1821): 353–68.


CD’s great interest in JS’s work on fertility of Primula crosses.

Thanks for Passiflora trials.

"By no means modify even in slightest degree any result."

CD wishes he had counted rather than weighed Primula seeds.

Letter details

Letter no.
Charles Robert Darwin
John Scott
Sent from
Source of text
DAR 93: B79; Linnean Society of London (Quentin Keynes collection)
Physical description
ALS 4pp encl Amem 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 4229,” accessed on 5 June 2023,

Also published in The Correspondence of Charles Darwin, vol. 11