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Darwin Correspondence Project

To Asa Gray   [3–]4 September [1862]1

Cliff Cottage. Bournemouth. Hants

Sept. 4th.

My dear Gray.

I have just received your most kind letter of Aug 18 & 19th 2 & will amuse myself, now my patients are in bed,3 by beginning a letter to you. My poor Boy (whose waxen face blushed up to the eyes at the thought of writing to a live Professor)4 has this day made a marked step & has taken several walks of a few hundred yards; & my wife is recovering well & her skin well peeling.— We have taken two houses here, so I hope & trust this dredful fever will not spread.—5 I am very glad that at present you intend to publish some separate notes on orchids, which you have so capitally worked out.6 No doubt I am not a fair judge; but I must think that it is worth your while.— I am pleased to hear about Goodyera & about Gymnadia tridentata. Your account makes me think the latter like the Bonatea speciosa & often & often have I speculated what on earth could be meaning of its wonderful horn-like stigmas & projecting anthers.7 I suspect its structure may have been arrived at by a process somewhat analogous to that which apparently has produced the wondrous nectary of Angræcum sesquipedale.8 It would appear that self-fertilisation is commoner than I thought: since publishing I have found that Neottia nidus-avis fertilises itself, if insects fail to do the job.—9 Many thanks for Houstonia seed.—10

I am glad to hear, but disappointed, about the Specularia pollen-tubes.11 I cannot resist sending you a diagram about Lythrum (why should I resist? does not prescription give a right? & have I not for long years written & bothered you about all sorts of things?) Lythrum has 3 kinds of stigmas & 3 kinds of pollen; the stamens of same height on two of the three forms producing the same sort of pollen, & I cannot doubt are fitted to fertilise the stigma of that height. I conclude so from watching the Bees; but hope to prove it by my crosses. So that we have three hermaphrodite forms each depending on half the stamens of either one of the two other forms. This is shown by the lines with the arrows. This strikes me as a very curious case. The three forms coexist in about equal numbers. By the way it seems to me that Lindley in Veg. Kingdom describes the homological structure of flower wrong:12 the so called calyx, with its 12 bundles of spiral vessels, appears to consist of 6 narrow sepals & 6 modified petals, all cohering; & that the coloured petals belong to an inner whorl & are modified stamens. By the way can you tell me of any flowers, with fertile anthers of different colours; I believe that this would be pretty sure guide to dimorphism or trimorphism.—13

All my semibotanical work, as you know, has been connected with insects, & now I am almost sure (but I find it a disgusting truth that with me first observations are generally all a blunder) that flowers have led me to a curious little discovery with respect to the best-known insect in the world, the Hive Bee. I saw the other day to my dismay (see Origin) Hive Bees sucking the common red clover, but it was a second crop, which I am told produces shorter flowers;14 but many of the Bees never attempted this, but always inserted their heads between the flowers & sucked at holes bitten through the corolla.— The same bee always followed the same practice. And apparently those which suck at the mouth of the flower have a longer proboscis than the other bees, which suck through the holes.

Farewell my dear Gray, forgive me scribbling about my own work; for I seldom see a soul to talk with on natural history.

Good night— Ever yours most truly | C. Darwin

Since writing the above by Jove I have found I have as usual at first blundered about the probosces; but if you had seen the Bees, the blunder was almost excusable—15 What an ass I was to scribble all the above.—

Progress of Education.— one of my little Boys Horace16 said to me, “there are a terrible number of adders here; but if everyone killed as many as they could, they would sting less”.— I answered “of course they would be fewer”   Horace “Of course, but I did not mean that; what I meant was, that the more timid adders, which run away & do not sting would be saved, & after a time none of the adders would sting”.—

Natural selection!!



The year is established by the relationship to the letter from Asa Gray, 18–19 August 1862. CD’s date was written in the top left-hand margin of the first page of the letter, and apparently represents the date on which the letter was completed. The relationship of this letter to the letter to John Lubbock, [3 September 1862] indicates that it must have been started before the letter to Lubbock, on the evening of 3 September 1862, and completed after that letter (see nn. 14 and 15, below).
Emma and Leonard Darwin were recovering from scarlet fever (see letter to John Lubbock, 2 September [1862] and n. 4).
Gray had sent a number of North American postage stamps for Leonard Darwin’s stamp collection (see letter from Asa Gray, 21 July 1862), and in his letter to CD of 18–19 August 1862, Gray suggested that Leonard should write to let him know what stamps he still required. A letter from Leonard was apparently enclosed with this letter (see letter from Asa Gray, 22 September 1862 and n. 3); however, the enclosure has not been found.
In the letter from Asa Gray, 18–19 August 1862, Gray described the occurrence in Gymnadenia tridentata of ‘an arm of stigma carried up each side of anther, & one between the [anther] cells’.
The reference is to the long nectary of Angraecum sesquipedale; in the specimens examined by CD, the nectary had been ‘eleven and a half inches long’ (Orchids, p. 197). In Orchids, pp. 202–3, CD provided the following explanation of the origin of the nectary: As certain moths of Madagascar became larger through natural selection in relation to their general conditions of life, either in the larval or mature state, or as the proboscis alone was lengthened to obtain honey from the Angræcum and other deep tubular flowers, those individual plants of the Angræcum which had the longest nectaries … , and which, consequently, compelled the moths to insert their probosces up to the very base, would be best fertilized. These plants would yield most seed, and the seedlings would generally inherit longer nectaries; and so it would be in successive generations of the plant and moth. In Orchids, p. 330, CD had suggested that the length of the caudicle carrying the pollinia in Bonatea speciosa had probably been ‘largely increased in length by natural selection’, rather than merely by the abortion of the lower pollen-grains.
In Orchids, CD had sought to demonstrate that the primary object of the various pollination mechanisms of orchids was to ensure cross-pollination (p. 1), and he noted only one case (Ophrys apifera) in which there were ‘special contrivances’ for self-pollination (p. 359); however, in his letter to CD of 18–19 August 1862, Gray reported that Gymnadenia tridentata provided a further example. Suspecting that Neottia nidus-avis might also be self-pollinating, CD had experimented with the species in May, comparing the seed-pods produced by a plant which had been covered to exclude insects, with those from an uncovered plant (see the notes, dated 17 and 21 May 1862, and 10 August 1862, in DAR 70: 73–4, 81). CD included this species on an undated list of ‘self-fertilisers’ that is now in DAR 70: 167, and also discussed it in his revised account of ‘self-fertilisation’ in Orchids 2d ed., p. 290.
In his letter to CD of 4 August 1862, Gray had expressed a hope that he would be able to send CD seeds of ‘the little Houstonia’; the seeds were probably enclosed with Gray’s letter of 18–19 August 1862.
Lindley 1853, pp. 574–5. Although CD’s copy of John Lindley’s Vegetable kingdom has not been found, this is the edition of the work listed in CD’s Library catalogue (DAR 240), and frequently referred to in Orchids.
See letter to John Lubbock, [3 September 1862], and letter to W. E. Darwin, [2–3 September 1862] and n. 5. In Origin, pp. 94–5, CD stated that hive-bees were unable to suck the nectar out of the flowers of the common red clover, which he claimed were ‘visited by humble-bees alone’ (see also Origin, p. 73). However, on the basis of information provided by Charles Hardy (see Correspondence vol. 8, letter from Charles Hardy, 23 July 1860), CD added the following statement to the third edition (p. 100): ‘I have been informed, that when the red clover has been mown, the flowers of the second crop are somewhat smaller, and that these are abundantly visited by hive-bees.’ In the fourth edition (p. 107), CD expressed some doubt about the accuracy of this statement, noting: That this nectar is much liked by the hive-bee is certain; for I have repeatedly seen, but only in the autumn, many hive-bees sucking the flowers through holes in the base of the tube which had been bitten by humble-bees.
Horace Darwin.
The diagram has been reduced to 50% of its original size.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Lindley, John. 1853. The vegetable kingdom; or, the structure, classification, and uses of plants, illustrated upon the natural system. 3d edition with corrections and additional genera. London: Bradbury & Evans.

Orchids 2d ed.: The various contrivances by which orchids are fertilised by insects. By Charles Darwin. 2d edition, revised. London: John Murray. 1877.

Orchids: On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. By Charles Darwin. London: John Murray. 1862.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.


Glad AG will publish some separate notes on orchids ["Fertilization of orchids through the agency of insects", Am. J. Sci. 2d ser. 34 (1862): 420–9].

Trimorphism in Lythrum.

Bee behaviour.

Letter details

Letter no.
Charles Robert Darwin
Asa Gray
Sent from
Source of text
Gray Herbarium of Harvard University (68)
Physical description
7pp sketch

Please cite as

Darwin Correspondence Project, “Letter no. 3710,” accessed on 10 July 2020,

Also published in The Correspondence of Charles Darwin, vol. 10