# To Francis Darwin   12 September [1878]1

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

Sept 12th.

My dear F.

I have been very glad to hear how you are getting on. It really seems that you must trust to your own observations alone on stomata.2 May not the stomata be variable even in the same species. Such variation may be expected in all characters which differ much in allied species of the same genus;3 & if I remember right the stomata do differ in the species of the same genus.— It certainly looks as if Sachs’ view was largely right,4 (surely some of your former cases were opposed to his view) but I cannot understand the length of time which Mer found that leaves could exist in water, especially with Ivy.5 How are stomata in Ivy?— I found also that leaves of Mimosa & Trifolium resupinatum lived long submerged.—6 I think that you will come to some interesting results.—

Yesterday I made a little observation which interested me: I put Drosera under the compound microscope, fastening back of old leaf with shell-lac to stick, & a tentacle did not circumnutate in the least during 7$\frac{1}{2}$ hours.; nor was it in the least heliotropic. I then touched secretion with atom of raw meat, not leaving any meat on gland, & in 23 seconds tentacle began to curve!7 I think we have observed enough to affirm that growth is always accompanied by circumnutation, & as the tentacle though so sensitive to animal matter did not circumnutate we may conclude that it was not growing; so Batalin must be wrong that the movement is partly due to growth.8

We see, also, how different such movements are to growth movements.— I wish you wd. make a note & enquire whether any Barbery bush in a pot is in flower in Kew; for I shd like to secure old flower to stick, & observe whether the sensitive stamens circumnutate.9 Lotus Jacobæus, I have just thought will be good to observe about pulvinus; for the cotyledon for first 4 or 5 days do not go to sleep, but do afterwards.10 Is pulvinus developed at first?

We are all well & fairly jolly, & all the jollier as Snow11 has gone.— Bernard12 is as sweet as sugar, but very contradictory. It grew wonderfully dark about half an hour ago; so I said “how dark it is”; so he shouted out “oh no”.— I then added I think it will soon rain, & he again shouted out “oh dear no” “oh dear no”.

I suppose the glass tubes will come tomorrow; but I won’t use them till your return.13

GoodBye dear old fellow | C. Darwin

## Footnotes

The year is established by the relationship between this letter and the letter from Francis Darwin, [12 September 1878].
See Origin 6th ed., pp. 119–20 (‘A Part developed in any Species in an extraordinary degree or manner, in comparison with the same Part in allied Species, tends to be highly variable.’
Julius von Sachs thought that bloom protected the stomata of plants from water (Sachs 1868b, p. 178; F. Darwin 1886, p. 99).
Émile Mer found that ivy leaves could survive several months under water, depending on conditions (see Mer 1876, pp. 243, 245, 247–52, 254, 255).
Trifolium resupinatum is Persian clover. CD’s son William had made some observations on submerged leaves; see Correspondence vol. 21, letter from W. E. Darwin, 30 August – 14 September [1873], Correspondence vol. 25, letter from W. E. Darwin, [12 or 19 July 1877].
See Movement in plants, p. 261.
Alexander Feodorowicz Batalin. See Batalin 1877; see also letter from Francis Darwin, [29 June] 1878.
Barberry bush, or Berberis; see Movement in plants, p. 132.
Lotus jacobaeus is the black-flowered lotus. See Movement in plants, p. 313.
Frances Julia Wedgwood, CD’s niece.
Bernard Darwin, Francis’s son.
See letter from Francis Darwin, [12 September 1878] and n. 2. Francis had sent glass tubes to be used in plant experiments.

## Bibliography

Batalin, Alexander Feodorowicz. 1877. Mechanik der Bewegungen der insektenfressenden Pflanzen. Flora, oder allgemeine botanische Zeitung 35: 33–9, 54–8, 105–11, 129–54.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Darwin, Francis. 1886. On the relation between the ‘bloom’ on leaves and the distribution of the stomata. [Read 4 February 1886.] Journal of the Linnean Society (Botany) 22 (1885–6): 99–116.

Mer, Émile. 1876. Des effets de l’immersion sur les feuilles aériennes. [Read 14 July 1876.] Bulletin de la Société botanique de France 23: 243–58.

Movement in plants: The power of movement in plants. By Charles Darwin. Assisted by Francis Darwin. London: John Murray. 1880.

Origin 6th ed.: The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 6th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1872.

## Summary

Julius von Sachs’s views on stomata seem largely correct, but CD cannot understand how leaves can survive submerged for such long periods.

Has been observing Drosera and concludes that none of the movement of the tentacles is caused by growth.

Suggests observations to show role of pulvinus in leaf movement.

## Letter details

Letter no.
DCP-LETT-11690
From
Charles Robert Darwin
To
Francis Darwin
Sent from
Down
Source of text
DAR 211: 45
Physical description
6pp