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Letter 2923

Darwin, C. R. to Oliver, Daniel

21 [Sept 1860]

    Summary Add

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    Lists of nitrogenous organic fluids that produce contraction in Drosera, and details of how to reproduce results.


Down Bromley Kent


My dear Sir

I am infinitely obliged for your note. The first thought which occurred to me was endosmose (& I tried olive oil & wine).— I have tried so many experiments that I cannot think I am in error. I rely much in the case of the saliva experiments on the diminishing effect of weaker & weaker doses. Sulphate & Muriate of Ammonia, Nitrate of Potash & N. of Lime produce none or hardly any effect. With respect to the Vegetable fluids I rely on nitrogenous fluid placed on the same leaves subsequently causing contraction, whereas the vegetable matters produced no effect.—

Nothing ought to be placed under the leaf as a support, for I have ascertained (in our Drosera) that irritation on the smooth under side of leaf causes contraction.

So small a drop ought to be put on as not to entangle the marginal hairs, as the act of drying of a viscid fluid mechanically draws the hairs together.—

Are you sure that there is no glue with your gum? I tried pure white gum & it produced no action at all. Nor did syrup of white sugar or starch.— For Heaven sake try some pure gum.— You have given me a panic. I tried

milk on 9 leaves thin Gelatine on 4 White of egg on 6 Saliva on 8 Urine on 11 Mucus on 4 infusion of meat 1 — 43 leaves.— and all strongly contracted on different plants

I have not tried vegetable fluid so largely only 3 or 4 leaves for each; for absolutely no effect was produced.

Believe me that I am truly grateful for your cautions.—

In Haste | Yours very sincerely | C. Darwin

I start for sea-side tomorrow, but letters will be forwarded to me.

P.S | Does not the sourness of your gum prove that it has fermented? And does not fermentation imply that there has been some nitrogenised matter in it? I am nearly sure that yeast is nitrogenised. Most cryptogamic plants certainly contain nitrogen.— For Heaven sake dissolve fresh pure, white gum & try again.

The inflection of disc of leaf itself, when it occurs is the best of all evidence.—

I fully believe, I have now ascertained that 12880 of grain of N. of Ammonia occasionally suffices with young & very sensitive leaf—, so that scrupulous care is requisite.—

    Footnotes Add

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    f1 2923.f1
    Dated by the reference to the Darwins' leaving for the seaside (see n. 6, below).
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    f2 2923.f2
    Letter from Daniel Oliver, 19 September 1860.
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    f3 2923.f3
    See letter from Daniel Oliver, 19 September 1860 and n. 3.
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    f4 2923.f4
    CD's notes on experiments to determine the effects of nitrogenous and non-nitrogenous fluids on the leaves of Drosera are in DAR 60.1. The experiments are described in Insectivorous plants, pp. 76--84.
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    f5 2923.f5
    When CD discussed this case in Insectivorous plants, pp. 77--8, he mentioned the problems of impurities in experimental samples of gum. He probably was referring to Oliver when he stated: `It is necessary to try pure gum arabic, for a friend tried a solution bought ready prepared, and this caused the tentacles to bend; but he afterwards ascertained that it contained much animal matter, probably glue.'
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    f6 2923.f6
    CD went to Eastbourne on 22 September 1860 (`Journal'; Appendix II).
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    f7 2923.f7
    Oliver wrote on the letter in pencil: `Some bits of clear gum picked'.
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    f8 2923.f8
    The postscript is on a separate slip of paper. The contents indicate that it belongs with this letter.
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