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Letter 4432

Scott, John to Darwin, C. R.

19 Mar 1864

    Summary Add

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    On fertilisation of Gongora.

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    His work on peloric Antirrhinum, Passiflora, and Verbascum, done at CD's suggestion, is at CD's disposal.

Transcription

Denholm

March 19th. 1864.

Sir,

I am surprised to find that your note of the 10th. ult. addressed to the Bot. Gar. has been returned to you, as I left my address with Mr. Mc.Nab… I am much obliged for your forwarding address to Mr. Kippist, I had quite neglected doing so. I had a note from Mr. Kippist sometime ago acknowledging receipt of missing portion of my M.S.

I am gratified to find that my Primula paper is ordered for the Journal, afraid, however, of harsh critic<isms> upon its many defects. I would have liked much Dr Hooker <to have> looked over M.S. before it had g<one to> the printers. <two or three words missing> made it more read<able> <    > now <several words missing><  >wing out of <several words missing>

I am glad to hear of corrob<orating> results fr<om> experiments, respecting the correctness <    > view on Catasetum. After the results of our exp<erime>nts on Acropera—considering the relative conditions of ovaria—I candidly speaking had doubts as to the absolute sterility of the Catasetum. If I am right however, in the following analogy, and the case been otherwise, viz, Catasetum susceptible to imperfect fertilisation, it would not have mattered much. In fact it would have afforded a more complete accordance between the phenomena of sterilisation by hybridity & these manifested in the graduated separation of the sexes. In the former cases we know that in general the sterilising effects are first manifested by the male organs (In a short paper which I have lately communicated to Bt. Soc. of Edin. on the Sexuality of the Higher Cryptogams as evidenced by the occurrence of hybrids I have mentioned the bigeneric hybrid known as Bryanthus erectus as a probable exception to this law), in the latter, or Catasetum case, we have an apparent analogy with the above in the rudimentary anthers of the Catasetum form, and the more perfectly developed placenta & ovules of the Monochanthus. Are you inclined to lay any stress on the above? perhaps I am quite wrong.

I am almost afraid to tamp<er with> the Acropera cases: they are most perplexing: the natural method of fertilization is singularly so <several words missing> rather in line <several words missing> <  >fore the fir<  > <several words missing> <f>lower inas<much> as I find the odd sepal freeing itself from <two words missing> from the base upwards; and cohereing with them <    > alone for sometimes several days previous to the expansion of the flower; so as to leave apertures in either side of the column sufficiently large for the bodily admission of the smaller insects, or a means of access for the larger. We might indeed suspect from the strong aromatic odour diffused by these plants in our hothouses during the night that they will be specially attractive to moths and other night-flying insects. Before fertilization they seem to offer no other attractions to insect visits, as I, like you have failed to detect a single drop of nectar; after fertilization, however, I find that in the Acropera Loddigesii and likewise the Gongoras atropurpurea and truncata an abundance of nectar exudes from the front of the column. This continues to be secreted even after the perianthal parts are entirely faded. (Have you observed this? I do not remember having observed it in any of the other genera of orchid on which I have experimented.) It is difficult to understand the meaning or use of this after-secretion of nectar, unless, indeed it be a provision in view of the difficulties attending effective fertilization: an in<ducem>ent f<or> insects to continue their visits, and <    > <obje>ct of their search be not obtain<ed> until <    > <req>uirements of the pl<  > <several words missing> make an estimate of <three or four words missing> produced by the different m<ethods> by which I <have> succeeded in fertilizing the Acropera <    >. Th<ere> is manifestly a decreased fertility by <cutt>ing off of the upper portion of column. By merely cutting off the clinandrum, however, I have nearly as fine looking capsules as those resulting either from the forcing in of the pollen-mass into the uncut stigmatic chamber; or by the immersing of them—pollinia—in viscous matter from other Orchids and applying them to stigmatic mouth. By the latter mode however, there is a very high per-centage of failures in the setting of the capsules; though in one or two of them thus produced are fine & plump… It is somewhat remarkable that the Gongoras should exhibit phenomena similar in every essential respect to those of Acropera!— I fear we will never fully understand these phenomena until we have opportunities of studying them in plants in their native habitats. I have a longing to be amongst them there.

I should have liked better if—health and time permitting—you had drawn up a paper on the above subject, and I would send notes with results of my experiments on A. Loddigesii & G. atropurpurea & truncata; so that with your own observations & experiments you <m>igh<t then> be enabled to give a most interesting paper. <two or three words missing> however, that you would rather not <    > in the work. I will as you have desired myself <three or four words missing> possibly insert it <    > <jo>urnal of B<otany> <    > have now no jour<nal> <    > which I cou<ld> communicate it. The Edin. N<ew Phil.> Journ. <is a> <com>plete failure. The April No. is its last & as for <the> Trans. Bot. Soc Edin. it would not then be seen for nine or ten months.— I suppose you will be communicating Dr Crügers paper to the Linn. Soc. immediately   in the case of my drawing up paper on Acropera might I notice his results—so far as relating to fertility of forms—as showing more forcibly the anomalous results of Acropera? I am busy drawing up tables of results of experiments of Peloric Antirrhinum Passifloras & Verbascums. Would your rather have me draw up independent papers on these? They were all undertaken at your suggestion, and now they are entirely at your service. If time had permitted you would indeed ere this have had them all. I will soon however have them prepared now.

I regret to find that you are still so weak; I trust you will improve as spring advances …

I am &c | J. Scott

    Footnotes Add

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    f1 4432.f1
    CD's note to Scott has not been found.
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    f2 4432.f2
    James McNab had been Scott's immediate supervisor before Scott left his post as foreman of the propagating department at the Royal Botanic Garden, Edinburgh (see letter from John Scott, 10 March 1864).
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    f3 4432.f3
    CD had evidently sent Scott's new address, included in the letter from John Scott of 10 March 1864, to Richard Kippist, librarian of the Linnean Society.
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    f4 4432.f4
    Scott refers to two pages of the manuscript of Scott 1864a that were found to be missing before it was printed in the Linnean Society's Journal; Scott had rewritten the pages (see letter from John Scott, 12 [February 1864] and nn. 4 and 5).
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    f5 4432.f5
    Scott 1864a was published in the Journal of the Linnean Society (Botany).
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    f6 4432.f6
    CD had been urging Joseph Dalton Hooker to take notice of Scott 1864a (see letter to J. D. Hooker, [20--]22 February [1864] and n. 6).
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    f7 4432.f7
    CD's letter to Scott relaying the results of Hermann Crüger's observations of Catasetum has not been found, but see the letter to Daniel Oliver, 17 February [1864]. Crüger had upheld CD's argument that the sexes were separate and that plants thought to be of different genera were actually different forms of the same species (see letter from Hermann Crüger, 21 January 1864, letter to Daniel Oliver, 17 February [1864] and n. 6, and Crüger 1864).
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    f8 4432.f8
    See also Correspondence vol. 11, letter from John Scott, [1--11] April [1863] and nn. 17 and 18, and this volume, letter to Daniel Oliver, 18 March [1864] and n. 8. CD discussed the conditions of ovaries in Acropera and Catasetum tridentatum in Orchids, pp. 207--8 and 237--8, writing that though the ovules of both genera appeared to be atrophied, the Acropera ovules seemed to be more atrophied. Scott discussed his observations of Acropera ovules in his letter of 11 November 1862 (Correspondence vol. 10); see also Correspondence vol. 11, letter from John Scott, 18 February [1863].
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    f9 4432.f9
    Scott read his paper `Remarks on the sexuality of the higher cryptogams, with a notice of a hybrid Selaginella' (Scott 1864c) to the Botanical Society of Edinburgh on 10 March 1864. See Scott 1864c, pp. 199--200, for his statement that `the pollen is more susceptible to the sterilising action than the ovules' and his exception (given in a note) to that statement.
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    f10 4432.f10
    In Orchids, pp. 242--4, CD discussed the rudimentary anthers of Monachanthus, which he argued was the female form of Catasetum; he described the more fully developed ovary of Monachanthus on p. 41.
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    f11 4432.f11
    CD's reply to this letter has not been found; however, he evidently expressed doubt about Scott's reference to Bryanthus as a bigeneric hybrid (see letter from John Scott, 28 March 1864 and nn. 2--4). In Origin, p. 265, in his discussion of hybrid sterility and sterility induced by changed conditions, CD wrote that in both cases the male structures of hybrids were `the most liable to be affected; but sometimes the female more than the male'.
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    f12 4432.f12
    For Scott's pollination of Acropera and his observations of the seeds produced, see n. 8, above. For CD's successful pollination of Acropera, see Correspondence vol. 11, letter to John Scott, 7 November [1863], and experimental note in DAR 70: 114.
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    f13 4432.f13
    CD and Scott were puzzled by how the narrowness of the stigmatic chamber and other structures of the Acropera flower could allow for insect pollination (see Orchids, pp. 203--6, Correspondence vol. 10, letter from John Scott, 11 November 1862, and letter to John Scott, 12 November [1862], and Correspondence vol. 11, letter to P. H. Gosse, 2 June [1863]). For CD's eventual conclusions on Acropera pollination, see Orchids 2d ed., pp. 166--73.
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    f14 4432.f14
    CD noted the lack of nectar in the flowers of several related orchids, including Acropera, in Orchids, pp. 282--3; however, his record of this observation is stated more strongly in Orchids 2d ed., p. 168. See Orchids 2d ed., p. 269, for CD's reference to Scott's noticing the lack of nectar. CD did suspect in 1862 and 1863 that insects gnawed the labellum for enclosed nectar in Acropera and related orchids (see Orchids, pp. 282--4, and Correspondence vol. 11, letter to P. H. Gosse, 2 June [1863] and n. 11). For CD's expanded conclusions about insect visits to Acropera and related orchids, supported by the observations of Hermann Crüger and Scott, see Orchids 2d ed., pp. 168--9 and 269--71, and the letter from Hermann Crüger, 21 January 1864.
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    f15 4432.f15
    CD recorded Scott's observation of nectar secretion after pollination in Acropera and Gongora in Orchids 2d ed., p. 168 n., adding that the exudation could `be of no use to the plant with respect to its fertilisation, and must be viewed as an excretion'.
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    f16 4432.f16
    Scott had succeeded in pollinating Acropera by cutting off the clinandrum, or the portion of the stigmatic column where the stamens were situated (see Balfour 1849, p. 202, and Orchids, pp. 121, 134). He devised this procedure when he pollinated Gongora truncata; he had earlier pollinated G. atropurpurea and Acropera by inserting pollen masses into the stigmatic chamber, sometimes with viscous matter from other orchids (see Correspondence vol. 10, letter from John Scott, 11 November 1862, and Correspondence vol. 11, letters from John Scott, 6 January 1863, [after 12] April [1863], and 21 May [1863]). For CD's reference to Scott's method of cutting off the clinandrum as a means of pollinating Acropera, see `Fertilization of orchids', p. 153 (Collected papers 2: 150), and Orchids 2d ed., pp. 169--70. CD mentioned Scott's earlier method of pollinating Acropera with the use of viscous matter from other orchids in Orchids 2d ed., pp. 169--70.
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    f17 4432.f17
    CD also wondered if the pollination and fertility of many tropical and subtropical orchids was affected by their being cultivated away from their native habitats (see letter to Daniel Oliver, 18 March [1864] and n. 7).
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    f18 4432.f18
    Some of Scott's comments on Acropera loddigesii, Gongora atropurpurea, and G. truncata were incorporated by CD in `Fertilization of orchids' and Orchids 2d ed.
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    f19 4432.f19
    The Edinburgh New Philosophical Journal was published from April 1826 to April 1864, and then merged with the Quarterly Journal of Science (see North 1989, 1: 494). Scott also refers to the Transactions of the Botanical Society [of Edinburgh].
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    f20 4432.f20
    See n. 7, above. CD communicated Crüger 1864 to the Linnean Society through Daniel Oliver in February (see letter from Daniel Oliver, 18 February 1864); the paper was read to the Linnean Society on 3 March 1864. Scott did not publish his results on Acropera pollination, but see n. 18, above.
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    f21 4432.f21
    CD encouraged Scott to experiment with Verbascum and Passiflora in 1862 and 1863 (see Correspondence vol. 10, letter to John Scott, 11 December [1862]; see also this volume, letters from John Scott, 7 January [1864] and n. 18, and [13 January 1864] and n. 7). Scott eventually published a paper on Passiflora that was communicated to the Linnean Society by CD (see letter from John Scott, 10 June [1864], and Scott 1864d). Scott published on Verbascum in 1867 (see letter from John Scott, 20 June [1864], Correspondence vol. 13, letter from John Scott, 21 July 1865, and Scott 1867).
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