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Darwin Correspondence Project

To Journal of Horticulture   [17 May 1861]1

Much obliged am I to Mr. Beaton for his very interesting answer to my question.2 When Mr. Beaton says he does “not know of an instance of the natural crossing of varieties,” I presume he intends to confine his remark to the plants of the flower garden;3 for every one knows how largely the varieties of the Cabbage cross, as is likewise the case (as I know from careful trial) with Radishes and Onions. It was this fact which led me to suppose that varieties of flower-garden plants would naturally cross.4

I can quite understand, after reading Mr. Beaton’s remarks, that it would be very difficult, perhaps impossible, to detect such natural crossing from the degree to which most of these varieties vary. I should, however, think that those who raise for sale seeds of distinct varieties of the Hollyhock, Stocks, &c., must know whether it is indispensable to keep the parent plants apart.5

I will not trouble Mr. Beaton again if he will have the kindness to procure for me answers on one or two points quoted in his paper (June 26, 1860) from the “king of British cross-breeders”—namely, whether I understand rightly that the white Anemone apennina seeding in a mass with the blue (Anemone apennina?) produced many pale shades?6 For this seems to be a case of two varieties naturally crossing, though I want to know the fact for another reason—namely, because Anemone does not secrete nectar; and secondly, whether Mathiola incana and glabra, which the writer speaks of as “crossing freely,” were artificially crossed.7

Mr. Beaton’s statement (July 24, 1860) that if the pollen of five kinds of Geranium (I presume what botanists call varieties, and not what are called species, are here referred to) are placed on the stigma of a flower, one kind alone takes the lead and produces an effect, seems to me a most curious observation. It is, I fear, unreasonable to ask for a few precise cases on this head; for, as I gather from Mr. Beaton, it must be difficult to know whether one or more kinds have produced an effect, owing to the great variability of crossed varieties.8

I have been delighted to observe how strongly Mr. Beaton insists that “not a flower in a thousand is fertilised by its own immediate pollen.”9 This is a subject which I have attended to for the last twenty years.10 From my experiments on a small scale I would not venture to put the case nearly as strongly as Mr. Beaton does; but on the other hand, some of the plants which Mr. Beaton advances as self-fertilisers seem, as far as I can trust my own observations, doubtful.11 I will give one instance, as it might possibly induce some one to try the experiment. Leschenaultia formosa has apparently the most effectual contrivance to prevent the stigma of one flower ever receiving a grain of pollen from another flower; for the pollen is shed in the early bud, and is there shut up round the stigma within a cup or indusium. But some observation led me to suspect that nevertheless insect agency here comes into play; for I found by holding a camel-hair pencil parallel to the pistil, and moving it as if it were a bee going to suck the nectar, the straggling hairs of the brush opened the lip of the indusium, entered it, stirred up the pollen, and brought out some grains. I did this to five flowers and marked them. These five flowers all set pods; whereas only two other pods set on the whole plant, though covered with innumerable flowers. The seeds in these pods were bad, or else I had not skill to make them germinate.12 I became so strongly convinced that insects would be found concerned in the fertilisation of these flowers, that I wrote to Mr. James Drummond, at Swan River in Australia, and asked him to watch the flowers of plants of this order; and he soon wrote to me that he had seen a bee cleverly opening the indusium and extracting pollen;13 and a bee with its mandibles thus covered with pollen would very likely effect a cross between one individual and another of the same species. I have been told that this pretty plant, the Leschenaultia formosa, never sets seed in this country. I wish some skilful cultivator would rout up the pollen within the indusium in the manner described, and see whether he could not thus get seeds.—14

Charles Darwin, Down, Bromley, Kent.

Footnotes

The date is established by the reference in the letter to C. W. Crocker, 18 May [1861] to CD’s having sent this letter off to the Journal of Horticulture ‘yesterday’. It was published in the issue of 28 May 1861 under the heading: ‘Cross-breeding in plants. Fertilisation of Leschenaultia Formosa.’ See also Collected papers 2: 42.
See letter to Journal of Horticulture, [before 14 May 1861]. Donald Beaton’s response to CD’s queries was published directly following the letter.
Beaton had written in response to CD’s previous letter (see n. 2, above) (Journal of Horticulture, Cottage Gardener, and Country Gentlemman n.s. 1 (1861): 113): My own experience of variable plants was given last week, and I do not exactly comprehend what is meant by natural varieties, for all the so-called varieties in cultivation have been artificially obtained either by a change of cultivation, or by crossing with pollen such kinds or species as would sport from seeds under cultivation. These kinds I call variable plants, their own progeny being constantly variable in aspect, and just as variable when the pollen of another flower is applied to them. It is a difficult thing for a gardener to see or comprehend the meaning of what botanists call varieties, or natural varieties of plants, because there is no limit, or sign, or any other indication in their outward aspect to distinguish them from the oldest species on record, and there is nothing in the botanical structure of even a variable seedling to distinguish it from a genuine species.
For CD’s efforts to ascertain information on this point through his own experiments and through queries to various botanists and practical gardeners, see Correspondence vol. 5, letters to William and Julius Fairbeard, [October 1855 – May 1856], and to J. S. Henslow, 10 November [1855] and 12 November 1855; and ibid., vol. 6, especially letter to J. D. Hooker, 19 July [1856].
Beaton included hollyhocks among those plants that he called ‘fixed varieties’, ‘as gardeners say when a variable plant comes true from seeds after sporting for some years’ (Journal of Horticulture, Cottage Gardener, and Country Gentleman n.s. 1 (1861): 112).
In his article on begonias in the Cottage Gardener, 26 June 1860, pp. 193–5, Beaton included the following statement on the authority of ‘the king of all the British cross-breeders’ (p. 194): ‘ “I have the white Anemone apennina, which some folks do not believe in, and many pale shades from its seeding in a mass with the blue.” ’
CD refers to Beaton’s statement that ‘Mathiola incana and glabra cross freely notwithstanding Darwin’s theory of species.’ (Cottage Gardener, 26 June 1860, p. 195).
The reference is to Beaton’s article entitled ‘Crossing flowers’, published in the Cottage Gardener, 24 July 1860, pp. 253–5, in which he disputed the scientific view of ‘superfoetation’, or the fertilisation of a plant ovary by two or more kinds of pollen. Beaton gave as a counter-example the case of fertilisation in geraniums (ibid., pp. 254–5): No flower on earth is more easy to prove by if more than one pollen can influence a cross than any of the common Geraniums. Their stigma is parted into five parts, and each part rolls back from the rest, or from the centre; and there are five seeds for every flower, corresponding to the five divisions of the stigma, or mother, as we say. Now, by applying five kinds of pollen, one kind to each division of the stigma, it is easy to conceive the possibility of each seed being influenced by that pollen only which dusted its corresponding division; and if the scientific explanation of the process by which the pollen reaches the ovum, or skeleton seed, were correct, superfœtation would be inevitable, and five kinds of progeny must be obtained from that flower so operated upon.
Beaton made this statement in his article of 14 May 1861 (Journal of Horticulture, Cottage Gardener, and Country Gentleman n.s. 1 (1861): 113).
See Notebook E, pp. 144, 183, and Questions & experiments notebook, pp. 2, 14 (Notebooks). See also Correspondence vol. 2, letter from William Herbert to J. S. Henslow, 5 April 1839.
Beaton listed among those flowers ‘every one of which must, of necessity, be fertilised by its own pollen in the great majority of instances’ sweetpeas, bellworts (Campanula), and wheat (see Journal of Horticulture, Cottage Gardener, and Country Gentleman n.s. 1 (1861): 113).
For descriptions of CD’s experiments, see Correspondence vol. 8, letters to J. D. Hooker, 18 [April 1860] and 26 April [1860], and letters from J. D. Hooker, [20 April 1860] and [28 April 1860]. The results of some of CD’s experiments on Leschenaultia are recorded in his Experimental book (DAR 157a).
See Correspondence vol. 8, letters to James Drummond, 16 May 1860 and 20 December [1860], and letter from James Drummond, 17 September 1860. The letter in which Drummond related this information, however, has not been found.
CD himself tried the experiment again in 1862 (see Correspondence vol. 10). He published a short note on the topic in 1871 (see Gardeners’ Chronicle and Agricultural Gazette, 9 September 1871, p. 1166; Collected papers 2: 162–5).

Bibliography

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. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Notebooks: Charles Darwin’s notebooks, 1836–1844. Geology, transmutation of species, metaphysical enquiries. Transcribed and edited by Paul H. Barrett et al. Cambridge: Cambridge University Press for the British Museum (Natural History). 1987.

Summary

Thanks Mr Beaton for his answer [to 3147].

Asks further questions on points raised in Beaton’s previous papers: whether crossing white and blue varieties of Anemone apennina produced many pale shades; whether the Mathiola incana and M. glabra which crossed freely were artificially or naturally crossed.

CD is delighted by Beaton’s assertion that "not a flower in a thousand is fertilised by its own immediate pollen".

Recounts his experiments with Leschenaultia formosa to show insect fertilisation.

Letter details

Letter no.
DCP-LETT-3162
From
Charles Robert Darwin
To
Journal of Horticulture
Sent from
Down
Source of text
Journal of Horticulture, Cottage Gardener, and Country Gentleman n.s. 1 (1861): 151

Please cite as

Darwin Correspondence Project, “Letter no. 3162,” accessed on 28 May 2020, https://www.darwinproject.ac.uk/letter/DCP-LETT-3162.xml

Also published in The Correspondence of Charles Darwin, vol. 9

letter