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Letter 3656

Darwin, C. R. to Gray, Asa

14 July [1862]

    Summary Add

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    Adaptations of orchid flowers. Believes the structure of all irregular flowers is adaptation to insect fertilisation.

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    Linum grandiflorum distinguishes its own pollen so that when placed on stigma of same flower the pollen-tube is not even exserted.

Transcription

Down Bromley Kent

July 14th

My dear Gray

I shd. have returned the enclosed sooner; but we have had had a miserable ten days. Our Boy (the Postage Stamp collector) has had a return of Scarlet fever, with all sorts of mischief, kidneys, glands of neck &c & still has much fever. But he is now made up for night & I will try & forget the misery of this weary world, & write a bit about science.—

With respect to Pogonia, it would be a very great anomaly, if insects open the anther for nectar: you say nothing about the rostellum; from Vanilla I shd. expect that viscid matter would be forced under lip of anther. Insects ought to be watched at work. In Australia Bees open the indusium of Goodeniaceæ for pollen.— Platanthera fimbriata is a pretty case. There is no end to the adaptations. Ought not these cases to make one very cautious when one doubts about the use of all parts?— I fully believe that the structure of all irregular flowers is governed in relation to insects. Insects are the Lords of the floral (to quote the witty Athenæum) world.— How well you have worked the N. American Orchids! I am heartily glad by this time that your harassing Lectures are over.

Hooker is very anxious about Mrs Hooker & has started on health-tour to Switzerland. Today I heard of the sudden death of poor old Prof. Bronn, just as he finished translating my orchid-book. There is misery & anxiety everywhere.— Poor dear Hooker seemed very anxious.—

A few days ago I made an observation which has surprised me more that it ought to do— it will have to be repeated several times, but I have scarcely a doubt of its accuracy.— I stated in my Primula paper that the long-styled form of Linum grandiflorum was utterly sterile with own pollen; & I have lately been putting the pollen of the two forms on the division of the stigma of the same flower; & it strikes me as truly wonderful, that the stigma distinguishes the pollen; & is penetrated by the tubes of the one & not by those of the other; nor are the tubes exserted. Or, (which is the same thing) the stigma of the one form acts on & is acted by (for the papillæ become colourless) pollen, which produces not the least effect on the stigma of the other form. Taking sexual power as the criterion of difference the two forms of this one species may be said to be generically distinct.—

Farewell my dear friend | C. Darwin

    Footnotes Add

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    f1 3656.f1
    The year is established by CD's reference to the death of Heinrich Georg Bronn (see n. 10, below).
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    f2 3656.f2
    The enclosure has not been found, but CD was probably returning some of Gray's notes on American species of orchids (see letter to Asa Gray, 1 July [1862]).
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    f3 3656.f3
    Entries in Emma Darwin's diary (DAR 242) for 5 and 6 July 1862 state that Leonard's `neck swelled' and that he was suffering from `bad symptom of kydney'. See also letters to W. E. Darwin, 4 [July 1862] and 9 July [1862]. In the letter to Asa Gray, 10--20 June [1862], CD had asked Gray to provide Leonard with several kinds of American postage stamp for his collection.
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    f4 3656.f4
    The observations by Gray on Pogonia to which CD refers have not been found; they were probably among the notes on American species mentioned in the letter to Asa Gray, 10--20 June [1862]. In DAR 70: 80, there is a note in CD's hand that reads: June 23d.   Asa Gray— Pogonia ophioglossoides— Pollen powdery loose grains, no threads— single grains   Pollen within a lid, he thinks insects lift this to get at nectar within! Does not mention Rostellum— At least it is clear that aid of some kind required.— See also letter to H. G. Bronn, 11 July 1862 and n. 4.
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    f5 3656.f5
    In 1860, CD had asked James Drummond, a botanical collector and one-time superintendent of the government gardens, Western Australia, to observe whether bees visited the flowers of Leschenaultia formosa, and, if so, whether they opened the lips of the indusium, or cup, at the top of the style; he also asked for similar information regarding any other members of the Goodeniaceae that possessed an indusium (see Correspondence vol. 8, letter to James Drummond, 16 May 1860; on Leschenaultia, see also this volume, letter to J. D. Hooker, 1 May [1862]). Drummond supplied CD with one instance of this sort (see Correspondence vol. 8, letter from James Drummond, 8 October 1860, and Correspondence vol. 9, letter to Journal of Horticulture, [17 May 1861]), by which CD confessed himself `extremely much interested' (Correspondence vol. 8, letter to James Drummond, 20 December [1860]).
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    f6 3656.f6
    Gray included an account of the adaptation for insect pollination of the floral anatomy of this species in the follow-up article to his review of Orchids (A. Gray 1862b, p. 424).
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    f7 3656.f7
    The reference may be to the review of Orchids that appeared in the Athenæum on 24 May 1862, pp. 683--5 ([Leifchild] 1862). The reviewer contrasted CD's pursuits with the fear of war between Britain and the United States, suggesting that `in the gardens of green and gladsome Kent', with a `philosopher's peaceful diligence', CD was principally occupied with his search for floral nectar while `half the world' was `experiencing or dreading the bitterness of war'. The phrase `Lords of the floral world' does not appear in the review; this may be CD's paraphrase of the reviewer's comments on the fertilisation of orchids (Athenæum, 24 May 1862, p. 685): the greatest care is taken throughout this vast order, …, that the pollen shall not be wasted; and yet, if we admit all Mr. Darwin's views, the act of fertilization is, with few known exceptions, left to insects.
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    f8 3656.f8
    Gray was Fisher Professor of natural history at Harvard University and lectured at the Lawrence Scientific School (Dupree 1959); for Gray's comments on his college duties, see the letters from Asa Gray, [2 June 1862], [late June 1862], and 2--3 July 1862.
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    f9 3656.f9
    Joseph Dalton Hooker had taken his wife, Frances Harriet Hooker, to Switzerland in the hope that she might recover her health (see letters from J. D. Hooker, 9 June 1862, 19 [June 1862], 28 June 1862, 2 July 1862, and 10 July 1862).
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    f10 3656.f10
    See letter from E. Schweizerbart'sche Verlagsbuchhandlung, 11 July 1862. In May and June 1862, Heinrich Georg Bronn had translated Orchids in preparation for a German edition (Bronn trans. 1862; see letter from H. G. Bronn, 21 June 1862); he died on 5 July 1862 (Quarterly Journal of the Geological Society of London 19 (1863): xxxii).
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    f11 3656.f11
    `Dimorphic condition in Primula', p. 96 (Collected papers 2: 63).
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    f12 3656.f12
    CD described these observations in detail in `Two forms in species of Linum', pp. 73--5 (Collected papers 2: 96--8), concluding: Taking fertility as the criterion of distinctness, it is no exaggeration to say that the pollen of the long-styled Linum grandiflorum (and conversely of the other form) has been differentiated, with respect to the stigmas of all the flowers of the same form, to a degree corresponding with that of distinct species of the same genus, or even of species of distinct genera. For CD's interest in the sterility of own-form crosses in dimorphic plants, see Correspondence vol. 10, Appendix VI.
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