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Darwin Correspondence Project

From Robert Caspary   18 February 1868

Koenigsberg in Pr.

18th of Febr. 1868

My dear Sir

I was thinking of writing to you, as I had heard nothing from you and of you for about 112 year, when your most kind present, the first part of your great and laborious work reached me.1 I give you my best thanks for it and I am very much obliged to you for it. As I dislike reading a translation of any work, which I am able to read in the original, I ordered directly the English original, but up to this time I received nothing. The booksellers say, that it is not yet published, which I also conclude from this, that up to this time I did not see the slightest notice of it in any English paper, which I take in, i.e. in 5 papers.2 So I delay reading your book till I have received the original English text, but I must not any longer delay thanking you for your kindness, as I did directly after the receipt of your present hoping to get soon the English original—

I wish and I hope, that you are, if not in good health, at least in tolerable one and that you will be able to work out still more of your valuable observations.

You remember, that we talked on Euryale ferox when I was with you,3 that the single flower a, fertilizes itself i.e. that flower a is fertilized by flower a, and I told you, that most generally the flower remains closed under water, but bears nevertheless just as good a fruit as if it had been opened above water— In 1865 I separated carefully the seeds of each flower of both sorts of behaviour and I found that both germinated very well, although I can not yet give the precise percents, having not yet worked up the numbers of seeds, which germinated and those, which did not germinate. In 1866 I grew two plants of Euryale from two seeds coming from two fruits, the flowers of which had kept under water and not opened. These two plants of 1866 were so large and really gigantic, that I never saw any thing like them— I earned from both together 1109 seeds—; from the one I examined 14, from the other 11 fruits. The mean of seeds of the single fruits were in one plant 31310, in the other 3319. 6 flowers in the other ones, not yet counted in, which opened, I fertilized myself with a brush, i.e. flower a was fertilized with flower b of another plant. But what was the consequence of this interference? These 6 flowers, artificially fertilized, had less seeds than those left to themselves, i.e. 27 23 in the mean— The fruit left to itself, had 67(!) seeds, a quantity of which I never saw any instance before in our green houses.4

Amongst Nymphaeaceae there are two sets of very different ways as regards fertilisation. A good many species want absolutely artificial fertilisation (flower a with flower b). All flowers left to themselves bear no seeds! The interior stamens opening last prevent mechanically the pollen of the outer ones, opening their anthers first, to get upon the stigma. Of this sort are: Nym. capensis, gigantea, flavovirens, dentata. Left to themselves the flowers of these plants kept far from insects and wind bring never a trace of a fruit; I saw 100s of flowers fade without giving any seed But on the other hand there are many species fertilizing themselves without the aid of insects or wind in the best way possible and giving the greatest quantity of good seed, just as many or even more as if fertilized artificially, these are: Nymphaea blanda, amazonum, Euryale ferox, Nymphaea Lotus, Nym. rubra.5 Finally there are some species, which fertilize themselves imperfectly, when insects and wind are excluded, but nevertheless bring many fruit and good seed: Nym. Caerulea [Par.] stellata Willd., ampla Hook., micrantha Hook.

My best regards to Mrs. Darwin, your two sons, whose personal acquaintance I made at your house and your daughter.6 I regret very much, that you are so far off. How much I should like to talk over with you a quantity of things, which I have at present at hand.

Believe me, my dear Sir, yours most truly and affectionately R. Caspary

CD annotations

1.1 I was … observations. 2.2] crossed pencil
3.1 Euryale ferox] underl pencil
3.8 In 1866 ] ‘x’ pencil
3.13 not yet counted] ‘x’ pencil
3.14 But … interference? 3.15] double scored pencil
Top of letter: ‘Fertility of Euryale & Nymphaea Dichog’ pencil; ‘given [mutability]red crayon; ‘fig Index of References | p 220’ blue crayon; ‘Inter [illeg] of the Papveraceæ’ pencil; ‘Water Lilies’ red crayon


Caspary’s name is on CD’s presentation list for the German edition of Variation (Carus trans. 1868; see Correspondence vol. 16, Appendix IV).
Variation was published on 30 January 1868 (see CD’s ‘Journal’ (Correspondence vol. 16, Appendix II)). The first reviews appeared in the second and third weeks of February ([Lewes] 1868a, [Robertson] 1868a).
Caspary had visited CD at Down on 27 May 1866 (see Correspondence vol. 14, Appendix II).
Caspary had previously shown that the unopened flowers of the waterlily Euryale ferox were able to set seed under water; he had advanced this case of self-fertility as a counter-example to CD’s theory of the necessity of occasional intercrossing between hermaphrodite individuals (see Correspondence vol. 14, letter from Robert Caspary, 25 February 1866). CD had tried to obtain seeds of the plant, and had asked others to perform crossing experiments to determine whether this aided fertility (ibid., letter to William Robinson, [29 April 1866], and letter to J. D. Hooker, 1 November [1866], and Correspondence vol. 15, letter to J. D. Hooker, 2 September [1867]). CD reported Caspary’s findings with E. ferox in Cross and self fertlisation, p. 365.
In Cross and self fertilisation, p. 365, CD wrote: ‘as I am informed by Professor Caspary [some species of Nymphaea] are quite self-fertile when insects are excluded’.
Caspary probably refers to Leonard and Horace Darwin, and to Henrietta Emma Darwin.


Discusses the flowers of, and cross- and self-fertilisation in, certain aquatic plants. Gives cases of dichogamy and perfect self-fertility.

Letter details

Letter no.
Johann Xaver Robert (Robert) Caspary
Charles Robert Darwin
Sent from
Source of text
DAR 76: B173–4
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 5894,” accessed on 20 June 2019,

Also published in The Correspondence of Charles Darwin, vol. 16