DCP-LETT-2985

# To Daniel Oliver   16 November [1860]1

## Nov 16th

My dear Mr Oliver

In writing out my paper yesterday I was so astounded at my results that I have got fairly frightened, & have determined to finish my paper, but to publish nothing until next summer2    I shall have retested my results & tried some of them in another way: so that there is no hurry about the Drawings.3 If there are good specimens, I shd be glad for Mr Fitch to complete them; otherwise will you ask him to wait till next spring or summer.—

Most heartily do I thank you for your most kind & valuable assistance.— If I could get one or two plants of Dionæa I would experimentise on them; but I shall not of course attempt the anatomy; & if you thought you would undertake the subject, I would not interfere in any way, except by bare allusions to what I have seen; but it is so important to me about the mottling or segregation of colour, that I shd. extremely much wish to ascertain that point, if in the Spring, by the aid of Mr Croker I could purchase (at almost any price) one or two or three of the young plants which he saw.—4

I have been corresponding with some of the chemical physiologists & as far as I can find out the curious action of the C. of Ammonia on the roots of plants has not been observed.—

With cordial thanks for all your kindness | My dear Mr Oliver | Yours very sincerely | C. Darwin

P.S. | Can you tell me name of Plant, which grew out of doors in my Fathers garden, 2 to 4 ft high—considerably branched, died down (I think) in winter, bore many minute almost white or very pale pink flowers, & which flowers caught a multitude of flies by their probosces.—5 I shd. like to get a plant to try to make out final cause of the catching.—

P.S. 2d. | Perhaps you would like to hear following extraordinary fact.— I have placed over & over again minute atoms of paper, stick, cinders meat flies &c on glands of single hairs of Drosera & they always became inflected; so I thought I would test how minute an atom would cause movement: I measured with micrometer several bits of woman’s Hair (& thread) which caused movement & found that under $\frac{1}{50}$ th of inch amply sufficed. Of same hair I sent 6 inches to be weighed in London by best balance, & it weighed under $\frac{1}{100}$ of grain, which shows that 1/30,000 of a grain suffices!!6

Prolonged pressure alone causes movement.

## Footnotes

1
Dated by the relationship to the letter to Daniel Oliver, 7 November [1860].
2
CD’s paper on Drosera was delivered at a meeting of the Philosophical Club of the Royal Society on 21 February 1861 (Bonney 1919, p. 154). It was not published, but CD ultimately included his earlier material in Insectivorous plants. His index for the paper is in DAR 54: 1.
3
CD had asked Oliver to find out whether Walter Hood Fitch would make drawings of Drosera for him (see letter to Daniel Oliver, 7 November [1860]).
4
Charles William Crocker was the foreman in the propagating department at the Royal Botanic Gardens, Kew.
5
Robert Waring Darwin, CD’s father, had been a keen gardener who cultivated a variety of rare and unusual plants in the gardens of The Mount, the Darwin residence in Shrewsbury (see Correspondence vol. 1).
6
See letter from Trenham Reeks, 15 November 1860.

## Summary

One thirty-thousandth of a grain of human hair inflects a single Drosera hair. Astonished by his results so he is not publishing until next summer. [Not published until 1875, Insectivorous plants. See ch. 2 for observations on inflection.]

Wants to study effects of acids on live Dionaea. Oliver should do their anatomy. Corresponding with chemical physiologists about carbonate of ammonia on roots.

## Letter details

Letter no.
DCP-LETT-2985
From
Darwin, C. R.
To
Oliver, Daniel
Sent from
Down
Source of text
Down House (MS 10: 26)
Physical description
6pp