Darwin Correspondence Project

Down, Bromley, Kent.

Aug. 5, 1860.

My dear Sir

I am infinitely obliged for your most clearly stated observations on the Bee-Orchis.^f1 It is now perfectly clear that something removes the pollen-masses far more with you than in this neighbourhood. But I am utterly puzzled about the foot-stalk being so often cut through.^f2 I should suspect snails. I yesterday found 39 flowers and of them only 1 pollen-mass in 3 flowers had been removed, and as these were extremely much withered flowers I am not quite sure of the truth of this. The wind again is new element of doubt. Your observations will aid me extremely in coming to some conclusion. I hope in a day or two to receive some day moths, on the probosces of which I am assured the pollen-masses of the Bee-Orchis still adhere.

Did you ever read D^r. Hooker’s paper in Philosph. Transactions, 1854, p. 259, on the curious structure of the Rostellum in Listera.^f3 D^r. H. is considerably mistaken about the use of the parts, but his facts are accurate; and it is following out the remarkable modification in the structure and function of the rostellum, that I am so anxious to examine Spiranthes and Epipactis and indeed all Orchids. The paper is really worth reading, though the facts in several respects are far more curious than Hooker suspected. I wrote yesterday to thank you for the Epipactis.^f4 For the chance of your liking to look at what I have found; take a recently opened flower, drag gently up the stigmatic surface, almost any object (the side of a hooked needle) and you will find the cap of the hemispherical rostellum comes off with a touch, and being viscid on under surface, clings to needle, and as pollen-masses are already attached to the back of rostellum, the needle drags out much pollen. But to do this, the curiously projecting, and fleshy summits of anther-cases must at some time be pushed back slightly. Now when an insect’s head gets into the flower, when the flap of the labellum has closed by its elasticity, the insect would naturally creep out by the back-side of the flower. And mark when the insect flies to another flower with the pollen-masses adhering to it, if the flap of labellum did not easily open and allow free ingress to the insect, it would surely rub off the pollen on the upper petals and so not leave it on stigma. It is to know whether I have rightly interpreted the structure of this whole flower that I am so curious to see how insects act. Small insects I daresay would crawl in and out and do nothing. I hope that I shall not have wearied you with these details.

With my cordial thanks Believe me | My dear Sir | Yours truly obliged | Charles Darwin

If you would like to see a pretty and curious little sight look to Orchis pyramidalis and you will see that the sticky glands are congenitally united into a saddle-shaped organ. Remove this under microscope by pincers applied to footstalk of pollen-mass and look quickly at the spontaneous movement of the saddle-shaped organs, and see how beautifully adapted to seize proboscis of moth.

Footnotes

f1

In Orchids, pp. 67–8, CD described an experiment performed by More on the bee-orchis (Ophrys apifera). More observed that `in plants growing singly both pollinia were invariably present. But on taking home several plants, from a large number growing in two places, and selecting plants which seemed to have had some pollinia removed, he examined 136 flowers: of these ten had lost both pollinia, and fourteen had lost one; so here there seems at first evidence of the pollinia having been removed by their adhesion to insects’.

f2

`Mr. More found no less than eleven pollinia … with their caudicles cut or gnawed through, but with their viscid discs still in their pouches, and this proves that some other animals, not insects, probably slugs, had been at work.’ (Orchids, p. 68).

f3

Hooker 1854b.

f4

See letter to A. G. More, 3 August 1860.