Darwin Correspondence Project

15 Marine Parade | Eastbourne

Thursday 27^th

My dear Sir

Your note of 25^th about the gum has been a great relief to me; for I took a panic, as I know I am very apt to blunder & run away with things. After writing to you I looked through my notes, & found I had been rather more careful, than I thought for I had tried 27 leaves with non-nitrogenised substances, not counting saline solutions & simple water. The more I reflect on the experiments which I have tried the less I think I am mistaken. Thus I fully expected that 1 gr of gelatine to oz. of distilled water, would have affected the leaves, but it produced no effect, whereas a little stronger solution produced a marked effect, & whereas 1 gr to 1 oz of several salts with nitrogen produced strong effect.— Thick syrup on 5 growing leaves produced no effect, whereas a leaf gathered & put into the same solution suffered in extraordinary degree from exosmose & the the hairs & disc of leaf collapsed; so that the vital power seems to resist exosmose in the living plant. I think I have made out the simple mechanism of movement.— But why I trouble you with all these details I know not.—

I will give you no more trouble, except that I earnestly hope you will try again the old gum; & if it acts, endeavour to find out certainly its composition. Thank you for the pretty leaf of the Australian Drosera; & for paper with gum; but I have a horrid cold & must stop to another day to try it: a large drop or 1⁄2 spoon-full dried & then put on heated knife is proper way to try.—

M. Trecul (I am so much obliged to you for telling me of that paper)^f2 disbelieves in any movement & accounts for flies being caught by their crawling under the gumy incurved hairs! But he kept the plants in a green-house or hot-house. Could this have paralysed them? I suppose not: anyhow hot-sunshine seems to make them act better. I imagine he looked out for sudden movement. Vapour of Chloroform for 30 seconds paralyses them completely.—

Thank you much for details of the unnamed Australian species. I will with permission quote your observations.^f3 Neither D. spathulata or the other species or D. longifolia seem to move quicker than D. rotundifolia.—

I am very glad to hear that you intend to attack spiny plants. Your note shows that it is a complex problem.—^f4

With many thanks. My dear Sir | Yours sincerely | C. Darwin

I have just received a cargo by Post of living plants of Drosera from Down & I will try more gum & starch myself.—^f5

In the unnamed Australian Drosera the incurvation of the leaf itself was terminal I suppose by your sketch. In D. rotundifolia, sometimes the incurvation is terminal; sometimes lateral; & sometimes termino-lateral, so as to be quite variable: as far as I saw in D. longifolia it was always terminal

Footnotes

f1

Dated by the relationship to the letter from Daniel Oliver, 25 September 1860.

f2

CD cited Tr´ecul 1855 in Insectivorous plants, p. 1 n. Oliver supplied the reference in a letter that is now missing (see letter to Daniel Oliver, 15 [September 1860]). Oliver’s note giving the reference is in DAR 60.1: 66.

f3

Oliver’s observations were given in the letter from Daniel Oliver, 25 September 1860. They were not cited in Insectivorous plants.

f4

Letter from Daniel Oliver, 25 September 1860.

f5

Notes on CD’s experiment, dated `Sunday 30<sup>th</sup>‘ and headed `Mr Olivers Gum from Kew, which will have caused contraction.—’, are in DAR 60.1: 110.