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Letter 3997

Scott, John to Darwin, C. R.

18 Feb [1863]

    Summary Add

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    Sends Acropera capsule for CD to dissect.

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    Will try to raise Acropera from seed (never done before in Britain) to examine its sexual forms.

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    Studying primroses, parthenogenesis, and reproduction of some cryptogams.

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    Received maize varieties from CD.

Transcription

Edinburgh | Botanic Gardens

18th. Feby

Sir.

In my last, I asked you if I might now send the capsule of Acropera, thinking it might be sometime before it matured. I am now, however, forced to do so, in consequence of its unexpected partial dehiscence. A few days before I last wrote, it changed colour slightly around the apex, this has slowly increased, though still as you will observe confined to the upper part. I, thus, had not the least suspicion of its bursting for some weeks at least, and I can assure you I was not a little vexed yesterday on observing what had happened, as I have thus lost a number of seeds. It is, I think, unusual to see them burst, before being at least partially coloured over. Perhaps the abnormalities of placentæ, utriculii, &c. which you first drew our attention to in this orchid, may have something to do with this. I will be anxious to hear the results of your dissection.

I have no doubt you will be somewhat astonished—though not entirely unprepared—on actually seeing the straight, plump capsule produced by Acropera, in view of your careful dissections; and certainly, fully justifiable deductions.

I have just placed a few seeds, which dropped into my hand, when I sent it off: under the microscope, a slight majority of these look to be quite perfect. These—30 or so—I will sow, and see if I can succeed in raising a few plants, which would be interesting as affording a chance for the solution of your query, as to what the other sexual forms of Acropera may be. This chance will be increased if—as I believe—it have never been raised from seed in this country, all its representatives being mere divisions of the originally imported plant. Now, believing, as I do, that merely vegetative multiplication will never render the slightest degree of permanency to a variation when tested by seeds. It will, I believe, from information I have been collecting on this point—after years of this kind of multiplication have as great a tendency to produce the form from which it originally sported, as it would if tried by seeds while still in organic connection with its parent, i.e. supposing a ``bud-variation.''

If then, Acropera, be as you are inclined to believe in a fluctuating state, we might expect some of the progeny at least to present the other forms. An important question, however, here presents itself. If Acropera be the male incipient form, and not yet perfectly sterile, will it when self-impregnated produce both forms? I am inclined to believe it will not. I think, I have indications of this in a variety of the Primrose in our gardens, all of which are long-styled. You, however, will be able to correct me on this point. I have great hopes that Parthenogenisis in plants, if established satisfactorily, will show this. I am led to hope for this result from my observation on the reproduction of variations in Cryptogams.

Excuse this hurried note. | I remain | Sir, | Yours very respectfully | John Scott.

I have just received your letter with varieties of Maize. I am glad that you have been able to afford me so many.

    Footnotes Add

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    f1 3997.f1
    The year is established by the relationship between this letter and the letter from John Scott, 3 March 1863.
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    f2 3997.f2
    Scott's letter has not been found; however, see the letter to John Scott, 16 February [1863] and n. 3. Dehiscence is the botanical term for the opening of a seed capsule.
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    f3 3997.f3
    Scott refers to CD's description of Acropera in Orchids, pp. 207--8.
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    f4 3997.f4
    CD had repeatedly failed in his attempts to effect pollination in two species of Acropera, namely, A. loddigesii and A. luteola. From this fact, and from dissections of A. loddigesii and A. luteola, CD deduced that all the flowers he had examined were male and had come from male plants, and that a female or hermaphrodite form of the same species must exist either under the same or under a different name (see Correspondence vol. 9, letter to Daniel Oliver, 30 November [1861], and Orchids, pp. 203--10). Additionally, CD's study of the related orchid Catasetum tridentatum, revealed that this species had three forms of flowers: male, female, and hermaphrodite (see `Three sexual forms of Catasetum tridentatum', and Orchids, pp. 236--48), which gave further credence to this interpretation. However, in November 1862, Scott wrote to CD informing him that he had succeeded in effecting pollination in A. loddigesii, by cutting open the stigmatic chamber and inserting the pollen masses (see Correspondence vol. 10, letter from John Scott, 11 November 1862, and letter to John Scott, 12 November [1862]), forcing CD to revise his earlier conclusion (see n. 5, below).
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    f5 3997.f5
    In Orchids, p. 209, CD remarked: What the female or hermaphrodite form of the Acropera luteola may prove to be—whether resembling in most respects the male, or whether it be at present named and masked as some distinct genus—it is impossible to say. After Scott had sent capsules of Acropera loddigesii containing viable seed, obtained by pollinating some flowers with pollen from the same plant, CD revised his earlier conclusion that the sexes in this genus were separate (see n. 4, above, letter to John Scott, 20 [February 1863], and `Fertilization of orchids', p. 153 (Collected papers 2: 150)).
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    f6 3997.f6
    Scott hoped to demonstrate that Acropera plants raised by vegetative division for a number of generations were more likely to reproduce individual variations than to reflect the normal range of forms of Acropera when produced by sexual reproduction. Scott and CD discussed at length the subject of variation and reproduction (see letters to John Scott, 21 January [1863] and 16 February [1863], and letter from John Scott, 3 March 1863). See also n. 9, below.
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    f7 3997.f7
    In his letter to Scott of 20 [February 1863], CD stated: `It is more likely that I have made some dreadful blunder about Acropera than that it shd be male not yet a perfect male'.
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    f8 3997.f8
    Throughout 1860 and 1861, CD had carried out a study of flower dimorphism and reproduction in Primula; he read his paper on the subject, `Dimorphic condition in Primula', before the Linnean Society on 21 November 1861. CD continued to work on the subject during 1862 (see Correspondence vol. 10, letter to John Scott, 19 November [1862]). See also letters to John Scott, 16 February [1863] and 20 [February 1863].
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    f9 3997.f9
    In a paper on fern spores read before the Botanical Society of Edinburgh on 12 June 1862 (Scott 1862a), Scott argued that there would be a greater tendency for individual variation in plants produced by asexual reproduction (including parthenogenesis) than in plants produced by sexual reproduction. Illustrating his point with reference to ferns, Scott reasoned that the fern spore, as `an independent self-developing organism', reproduced the peculiarities of the organ on which it originated, hence explaining the `peculiar power which the spore possesses for the reproduction of accidental variations' (Scott 1862a, pp. 216--18). See also Correspondence vol. 10, letters from John Scott, 15 November [1862] and 17 December [1862], and this volume, letter from John Scott, 16 January 1863.
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    f10 3997.f10
    In his letter to Scott of 16 February [1863], CD sent specimens of North American maize seeds (see letter to John Scott, 16 February [1863] and n. 9).
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