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Letter 5012

Darwin, C. R. to Caspary, J. X. R.

21 Feb [1866]

    Summary Add

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    Requests copy of paper read at Amsterdam Horticultural Congress, on graft-hybrids like that of Cytisus adami [see 5018].


Dear Sir

I hope you will excuse the liberty which I take in begging a favour of you. You read a paper at the Amsterdam Hort: Congress on cases like that of Cytisus Adami. Would you have the kindness to tell me where this has been, or will be, published? and if you have a spare copy I should be grateful for it. If you do not intend to publish it I beg you not to take the trouble to answer this note as I shall understand your silence.

I am very much interested in this subject which I hope you will receive as some excuse for my troubling you.

With very sincere respect I beg leave to remain | Dear Sir | yours faithfully | Ch. Darwin

Down Bromley, Kent | Feb. 21st.

    Footnotes Add

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    f1 5012.f1
    The year is established by the relationship between this letter and the letter from Robert Caspary, 25 February 1866.
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    f2 5012.f2
    Caspary delivered the paper on Cytisus adami (now +Laburnocytisus adamii) and other hybrids that he believed were produced by grafting at the International Congress of Botany and Horticulture held at Amsterdam from 7 to 12 April 1865 (Caspary 1865a). CD had read a notice of the paper in the Gardeners' Chronicle, 29 April 1865, p. 386 (see Correspondence vol. 13, letter to J. D. Hooker, [1 May 1865], and letter from M. T. Masters, 12 July 1865). The paper appeared in Bulletin du Congrès International de Botanique et d'Horticulture réuni à Amsterdam (1865): 65--80; CD's offprint of the paper, bound with an annotated handwritten English translation, is in the Darwin Pamphlet Collection--CUL.
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    f3 5012.f3
    CD had long been interested in Cytisus adami (now +Laburnocytisus adamii), a hybrid produced by grafting a scion of Cytisus purpureus (a dwarf purple broom) onto a stock of Laburnum anagyroides (the common yellow laburnum). See Correspondence vols. 4--6, 10, and 11. Unlike most grafts, which preserve the floral character of the scion, +L. adamii has branches of purplish-yellow flowers, which regularly revert to those of both parent species (Bean 1970--88, 2: 510--11). CD had tried to propagate the hybrid by seed, and to produce the hybrid by crossing, but without success (see Correspondence vol. 6, letter to J. D. Hooker, 8 September [1856], and Correspondence vol. 10, letter to Daniel Oliver, 24 July [1862]). CD discussed the plant in Variation 1: 387--97, 405--11, and 2: 37, 364--5, noting the `extraordinary fact' that two distinct species could `unite by their cellular tissue, and subsequently produce a plant bearing leaves and sterile flowers intermediate in character between the scion and stock, and producing buds liable to reversion; in short, resembling in every important respect a hybrid formed in the ordinary way by seminal reproduction' (Variation 1: 390). He argued that the plant was a graft-hybrid, and not a product of sexual union, citing Caspary 1865a and other information obtained from Caspary's letters (Variation 1: 388--9). Because it displayed both fusion and reversion of characters, +L. adamii served to illustrate the similarity of asexual and sexual modes of reproduction, an important aspect of CD's theory of pangenesis (see Variation 1: 411, 2: 364--5, and Olby 1985, pp. 76--80).
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