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Darwin Correspondence Project

To Francis Darwin   30 July [1878]1

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

July 30th

My dear old Backy

I am very sorry you have been again “slack”. Your 2 last letters very interesting & valuable, & you have got a fine lot of knowledge out of Sachs. But you are an impudent dog, as the beginning of your last note shows.—2

I shd. be very glad to see De Vries here, but we leave home on the 7th. & shall be away about 3 weeks; though if Fanny Hensleigh shd. come here soon, we may, I suppose have to alter our plans. about returning.— Tell Vries this if you see him.3

Observe, if you can, whether the water obtains anything from the bloomless or cleaned petals of Helvingia.4 If you have any flowers, you might hang up a few cleaned & uncleaned about relative shrivelling or drying.—

Sachs remark about the stomata seems very important; yet I can hardly understand how with M. Mer the leaves of so many plants kept alive for many days or even weeks when fairly immersed in water. I thought that each leaf chiefly depended on its own power of breathing & nourishing itself. I wonder what Sachs wd. say to Mer’s statements.—5

I quite agree with what Sachs says that certain actions of plants or effects on them are neither advantageous or disadvantageous: unless, for instance, light produced some tendency to move or some effect, there could have been no beginning to acquiring perfect heliotropism or apheliotropism.—6

My Porliera was last watered on July 6th & yesterday it seemed dying; but the leaves have never slept during the day, even not those on twig in bottle with quick-lime. It did not even sleep last night from “dry rigidity”, but recovered when watered with wonderful quickness.— My notion now is that agitation from wind & dryness is cause of the diurnal sleep.—7

Your affect Father | C. Darwin

Your observations on manner of growth of free & coiled twiners seems eminently well worth investigation.—8

I wrote on double paper by mistake9


The year is established by the relationship between this letter and the letter from Francis Darwin, 24 and 25 July 1878.
See the letter from Francis Darwin, 24 and 25 July 1878, reporting being unwell and also his conversations with Julius Sachs. The second letter from Francis, with the impudent beginning, has not been found.
Hugo de Vries was working in Sachs’s laboratory in Würzburg. The Darwins visited family in Surrey and Staffordshire between 7 and 22 August 1878 (CD’s ‘Journal’ (Appendix II)). The only mention of Frances Emma Elizabeth Wedgwood in Emma Darwin’s diary for August 1878 is a note on 23 August recording ‘Fanny H. v. poorly’ (DAR 242). In the event, De Vries visited CD at the home of Thomas Henry Farrer in Abinger, Surrey (see letter to Hugo de Vries, [15] August [1878]).
Sachs had shown Francis the fruit of Helvingia ruscifolia (a synonym of Helwingia ruscifolia); Francis had suggested that the petals, which closed over the carpel, might be covered with bloom because they acted like a part of the fruit (see letter from Francis Darwin, [21 July 1878]).
Sachs suggested that leaves wanted to keep dry in order to keep their stomata open to breathe (see letter from Francis Darwin, 24 and 25 July 1878). Émile Mer had suggested that submerged leaves could survive as long as they continued to produce starch, and that various factors such as species, age, temperature, etc., affected this ability (Mer 1876, pp. 257–8).
Plants of Porlieria in Würzburg were observed to sleep even during the day, while the plant CD borrowed from Kew did not. At first CD had assumed daytime sleep was caused by dry conditions, but his observations on the Kew plant did not support this view (see letter from Francis Darwin, 24 and 25 July 1878 and n. 1). Francis, having seen a twig sent by CD, suspected the plants in Würzburg were not the same species as the one from Kew (see letter from Francis Darwin, [after 7 July 1878] and n. 3).
This may be a reference to the missing letter from Francis Darwin (see n. 2, above).
CD did not realise that two sheets were stuck together when he turned over the paper to write on what he thought was the verso of the first page. He then used the verso of the first two pages to write the remainder of his letter.


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.


Comments on function of bloom.

Describes the effect of water shortage on sleep movements in Porlieria.

Letter details

Letter no.
Charles Robert Darwin
Francis Darwin
Sent from
Source of text
DAR 211: 41
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 11635,” accessed on 21 June 2024,