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Darwin Correspondence Project

To Asa Gray   13 September [1864]1

Down. | Bromley. | Kent. S.E.

Sept 13th

My dear Gray

I have taken a long time to thank you for your pleasant & most friendly note of July 11th;2 I am not ungrateful, but I have less strength (though still gaining some & now at last living down stairs) than formerly & after my two hours work glad to be quite idle. I have little to say; for my soul has been absorbed with Climbing plants, now finished3 & tomorrow I begin again, after 13 months interruption on “Variation under domestication”.—4

I received lately a Review on H. Spencer with the address in your handwriting; I like much all the latter part; but surely you did not write it?5 If you did you had muddled your brains (in the first part) by reading metaphysics & all elasticity had gone out of your style.— Oh, if you did write it, shall I not have some nice little stabs with your smooth dagger! I also before received a review on Dana,6 I believe in your handwriting; & this interested me considerably & I thought it was perhaps by you.— I write now chiefly to say that I send by this paper a paper which has interested me greatly by a gardener John Scott;7 it seems to me a most remarkable production though written rather obscurely in parts, but worth the labour of studying.— I have just bethought me that for the chance of your noticing it in the Journal,8 I will point out the new & very remarkable facts.— I have paid the poor fellow passage out to India, where I hope he will succeed, as he is a most labourious & able man, with the manners, almost of a gentleman.—9

We are profoundly interested by your politics; & do not in the least know whether the “old Bloody Times” is to be trusted that there will be peace & that the middle States will join with the South on Slavery & eject the northern states.—10 In the latter case, I hope you will marry Canada, & divorce England & make a grand country, counterbalancing the devilish South—

Yours affectionately | Charles Darwin


Scott’s paper

p. 106–108. Red cowslip by variation has become non-dimorphic, & with this change of structure has become much more productive of seed than even the heteromorphic union of the common cowslip.—11

p. 91–92 similar case with Auricula— On other hand a non-dimorphic var. of P. farinosa (p. 115) is less fertile. These changes or variations in the generative system seem to me very remarkable.12

But far more remarkable is the fact that the Red Cowslip (p. 106–8) is very sterile when fertilising,, or fertilised by, the common cowslip. Here we have a new “physiological” species.—13 Analogous facts given (p. 98) on the crossing of Red & White Primroses with common Primroses.—14

It is very curious that the two forms of the same species (p. 93, 94, 95, & p. 117) hybridise with extremely different degrees of facility with distinct species.—

He shows (p. 94) that sometimes a cross with a quite distinct species yields more seed than a homomorphic union with own pollen.

He shows (p. 111) that of the two homomorphic unions possible with each dimorphic species; that the short-styled, (as I stated) is the most sterile, & that my explanation is probably true.15 There is good Summary to Paper.—16


The year is established by the relationship between this letter and the letter from Asa Gray, 11 July 1864.
According to CD’s journal, the manuscript of ‘Climbing plants’ was finished on 13 September 1864, and CD returned to his manuscript of Variation on 14 September 1864 (see ‘Journal’ (Correspondence vol. 12, Appendix II)). However, CD continued making observations and adding to the manuscript of ‘Climbing plants’ until the end of the year (see letter to Asa Gray, 29 October [1864], and letters to J. D. Hooker, 4 December [1864] and n. 10, and 10 December [1864] and n. 6). ‘Climbing plants’ was read at the Linnean Society on 2 February 1865. For the manuscript, see DAR 17 and DAR 18.
According to his journal, CD had not worked on Variation since 20 July 1863 (see Correspondence vol. 11, Appendix II, and this volume, Appendix II). CD began writing Variation in 1860 (see Correspondence vol. 8, Appendix II).
The reference is to a review of Spencer 1864b; the review was by Chauncey Wright ([Wright] 1864b). See letter from Asa Gray, 3 October 1864.
James Dwight Dana. The reference is to Gray’s anonymous review of Dana 1864b ([Gray] 1864) see letter from Asa Gray, 3 October 1864 and n. 5).
The reference is to John Scott’s paper ‘Observations on the functions and structure of the reproductive organs in the Primulaceæ’ (Scott 1864a); there are annotated copies of this paper in the Darwin Pamphlet Collection–CUL, and among CD’s unbound journals in the Darwin Archive–CUL. For a discussion of CD’s role in stimulating Scott to research and write this paper, see the letter from John Scott, 7 January [1864] and nn. 2–5.
Gray regularly wrote reviews of botanical works for the American Journal of Science and Arts; his review of Scott 1864a, which drew attention to the ways in which Scott’s work confirmed CD’s observation, appeared in the January 1865 issue of the journal (Gray 1865).
John Scott had been without employment since leaving his position as foreman of the propagating department at the Royal Botanic Garden, Edinburgh, in March 1864 (see letter from John Scott, 10 March 1864). Joseph Dalton Hooker had suggested that Scott seek a position in India in his letter to CD of 19 May 1864, and CD wrote to Scott to offer him the financial assistance required to make the journey (see letter to John Scott, 21 May [1864]). See also letters from John Scott, 28 May [1864], and 2 August 1864 and nn. 1 and 2. Scott visited CD at Down House in August before leaving for India (see letter to J. D. Hooker, [16 August 1864], n. 2).
In early September 1864, The Times reported on the growing movement of public opinion in America towards peace, and the divisions amongst the Union’s political representatives on the armistice issue (see, for example, The Times, 3 September 1864, p. 6, 8 September 1864, p. 6, and 9 September 1864, p. 7). An editorial in The Times on 13 September 1864, p. 8, predicted that if Abraham Lincoln were re-elected in the forthcoming presidential elections, the Civil War would continue, with the prospect of the secession of the ‘great Western States’. For a discussion of the public desire for peace in the northern states and the pressures on Lincoln during August and early September 1864, see McPherson 1988, pp. 760–1 and 768–71. For CD’s opinion of the standard of reporting of the American Civil War in The Times see Correspondence vol. 10, letter to Asa Gray, 16 October [1862], and Correspondence vol. 11, letter to Asa Gray, 23 February [1863] and n. 23.
In Scott 1864a, pp. 106–8, Scott presented the results of experimental crosses with three flower forms of cowslip (Primula veris): an equal-stamened and equal-styled, or non-dimorphic, red variety of cowslip, a long-styled form of the common cowslip, and a short-styled form of the common cowslip. Scott’s tabulated results (p. 106) suggested that the self-pollinated non-dimorphic red cowslip produced more seed, and was therefore likely to be more fertile, than the long-styled cowslip crossed with the short-styled cowslip (representing a ‘heteromorphic union’). Scott discussed the non-dimorphic cowslip in his letter of 21 May [1863], and enclosed seeds from this plant with his letter of [26 July – 2 August 1863] (Correspondence vol. 11). See also letter from John Scott, 7 January [1864]. In 1864 and 1865 CD made observations of cowslip pollen, including pollen from plants grown from Scott’s seed (see memorandums from W. E. Darwin, [30 April 1864] and [after 19 May 1864]. In 1865 and 1866 CD repeated the experiments with the seed sent by Scott, and confirmed the high degree of self-fertility of this form of P. veris. CD’s results with the red cowslip are discussed in Variation 2: 109 n. and ‘Illegitimate offspring of dimorphic and trimorphic plants’, pp. 426–30. See also n. 13, below. CD’s notes on these experiments are in DAR 108: 99–124.
CD commented on Scott’s observations of Primula auricula and P. farinosa in ‘Illegitimate offspring of dimorphic and trimorphic plants’, pp. 418–19, and Forms of flowers, pp. 223–4.
When CD repeated Scott’s experiments with the non-dimorphic form of red cowslip (see n. 11, above), he was unable to corroborate Scott’s finding that the form exhibited a high degree of sterility when crossed with other forms. See also Cross and self fertilisation, pp. 222–5, and DAR 78: 4 v. and 65–8. Sterility had long been regarded as a test of true species, and Thomas Henry Huxley had coined the term ‘physiological species’ to describe animals or plants that exhibited cross or hybrid sterility (T. H. Huxley 1863b, pp. 106–8). CD had been challenged by Huxley to demonstrate a case of artificial selection producing varieties of a species that were cross sterile, that is, new ‘physiological’ species (see [T. H. Huxley] 1860, T. H. Huxley 1862, pp. 108–13, 146–50, and T. H. Huxley 1863b, pp. 107–8). CD’s interest in cases of intra-specific sterility was in part prompted by this challenge. See Correspondence vol. 10, Appendix VI, and Correspondence vol. 11, letter to T. H. Huxley, 10 January [1863].
CD refers to Scott’s crossing experiments with Primula vulgaris, P. vulgaris var. alba, and P. vulgaris var. rubra, which Scott presented as analogous cases of intra-specific sterility. CD discussed these experiments in Variation 2: 109 n., ‘Illegitimate offspring of dimorphic and trimorphic plants’, p. 420, and Forms of flowers, pp. 224–5. CD repeated the crossing experiments with P. vulgaris var. rubra in 1865 and 1866 using seeds sent by Scott with his letter of [26 July – 2 August 1863] (Correspondence vol. 11), but his results did not confirm Scott’s conclusion that the variety was sterile when pollinated by the common primrose. CD’s notes on these experiments are in DAR 108: 89–98 and DAR 110: 2–4.
CD’s explanation for the greater sterility of the short-styled homomorphic unions of dimorphic species was given in ‘Dimorphic condition in Primula, p. 93 (Collected papers 2: 60): the chance of self-fertilization is much stronger in this [the short-styled form] than in the other form [the long-styled form]. On this view we can at once understand the good of the pollen of the short-styled form, relatively to its own stigma, being the most sterile; for this sterility would be the most requisite to check self-fertilization, or to favour intercrossing. In the short-styled form the anthers bearing the pollen are positioned above the stigma, making it more likely that pollen would fall on the plant’s own stigma than in the long-styled form, where the anthers are positioned below the stigma. CD had come to believe that most plants were adapted to promote the intercrossing of distinct individuals.


‘Climbing plants’: On the movements and habits of climbing plants. By Charles Darwin. [Read 2 February 1865.] Journal of the Linnean Society (Botany) 9 (1867): 1–118.

Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

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

Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.

‘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.

[Gray, Asa.] 1864. [Review of A text-book of geology, by J. D. Dana.] American Journal of Science and Arts 2d ser. 37: 147–8.

[Huxley, Thomas Henry.] 1860a. Darwin on the origin of species. Westminster Review n.s. 17: 541–70.

‘Illegitimate offspring of dimorphic and trimorphic plants’: On the character and hybrid-like nature of the offspring from the illegitimate unions of dimorphic and trimorphic plants. By Charles Darwin. [Read 20 February 1868.] Journal of the Linnean Society of London (Botany) 10 (1869): 393–437.

McPherson, James M. 1988. Battle cry of freedom: the Civil War era. New York and Oxford: Oxford University Press.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Has finished Climbing plants;

resuming work on Variation.

Sends abstract of John Scott’s paper [see 4332].

Has received review of Herbert Spencer but cannot believe AG wrote it unless he has muddled his brains with metaphysics.

Letter details

Letter no.
Charles Robert Darwin
Asa Gray
Sent from
Source of text
Gray Herbarium of Harvard University (89)
Physical description
ALS 6pp, encl 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 4611,” accessed on 21 June 2024,

Also published in The Correspondence of Charles Darwin, vol. 12