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Letter 2805

Darwin, C. R. to Henslow, J. S.

17 May [1860]

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    Sends characters by which he can divide all primroses and cowslips into what he suspects will be male and female plants. Believes these forms are first step in formation of a dioecious plant.

Transcription

Down Bromley Kent

May 17th

My dear Henslow

Many thanks for your note & information about my opposers.— I have sent for Literary Gazette.—   For the chance of your caring I send the characters by which I can divide all Primroses & cowslips into what I suspect will turn out Male & Female Plants. These two forms exist in about equal numbers.—   I have marked a set of both forms to see about seeding. The difference in state of pollen is very clear & invariable.

I suspect it will turn out fine case for me: the first gradation in the formation of a dioicous plant.—   The Holly forms a second step, for here the male plant has anthers but no pollen.— The male cowslips have abundant pollen, but all grains small-sized.—

It will be curious if I can show that so common a plant is dioicous or nearly so.

Auriculas are in same state as far as I have seen.—

This is reason why I wanted to know whether you had observed long & short pistils in any other flowers.

Yours affectly | C. Darwin



[Enclosure: 1]

*uCowslips Primroses MalePlants. Tube of corolla long, throat short— Stamens long— pollen in water about 96000 of inch in diameter. Pistil short, stigma far beneath anthers,— surface of stigma smoother Female plants:— Tube of corolla short, throat long.— Stamens short, pollen in water about 66000 of in inch in diameter.— Pistil long, stigma far above anthers, surface of stigma rougher.—

    Footnotes Add

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    f1 2805.f1
    The Literary Gazette, 12 May 1860, p. 582, included a report on Adam Sedgwick's and William Clark's remarks about Origin at the Cambridge Philosophical Society meeting on 7 May 1860.
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    f2 2805.f2
    See letter to J. S. Henslow, 14 May [1860].
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    f3 2805.f3
    In CD's paper on the dimorphic condition of Primula, read on 21 November 1861, the measurements were changed to 10-11/7000 of an inch for the pollen from short-styled plants and 77000 of an inch for that from the long-styled plants. By the time CD wrote this paper, he had found that the short-styled plants produced more seeds than the long-styled, and so he designated the short-styled ones `females'. See Collected papers 2: 49--51.
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