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Darwin Correspondence Project

From W. C. Marshall   5 September [1874]1

Derwent Island | Keswick

Saturday Sep 5th.

Dear Mr. Darwin

I am sending you by tomorrow’s post some more leaves of Pinguicula wh. have seeds on them for the most part. I also enclose a list from wh. you will see that 79 per cent of the leaves I have examined had insects on them.2 I have counted the remains of insects wh. had apparently been some time on the leaf & many small things wh. I cd. not have recognised as insects without the aid of a magnifying glass.

I have also counted in several small spiders. The insects were for the most part small gnats & aphides, but there seemed to be a great variety, I have found a few beetles, but no moths. The observations have been made during an exceptionally rainy week, with an average daily rainfall of 34 of an inch!! Pinguicula Vulgaris grows in wet places on mountain slopes, & has as far as I have observed a partiality for running water. The following are some of the more conspicuous plants tt. grow with it—

Parnassia Palustris

Drosera Rotundifolia

Saxifraga aizoides

Anagallis tenella

Erica tetralix3

With regard to the secretion from insects, I can not trace it; I observe fluid on the leaves, generally in the chanel formed by the edge; but whether this is a secretion of the plant, or from the insect, or merely rain water lodged, I can not tell; but it is certainly sticky, & therefore if rain water must have disolved some of the viscid matter of the points on the leaves.4

I have observed tt. the leaves are not unfrequently eaten as if by slugs.

Also I have no doubt you have noticed tt. there is a tendency in the leaves to curl tightly over entrapped insects that get near the edge, & the same applies to seeds.5 I have noticed brown patches & in one or two cases holes under insect remains, I supose this is the result of over manuring, I have noticed the same effect on grass; I mean the excrement of animals kills grass where it lies but forms luxuriant growth of grass round.

I have, I fear, put my remarks in a rambling & inconvenient form. If there is anything I have not answered distinctly, please get Horace to write me a note about it6

Believe me | yrs. very truly | William C. Marshall

CD annotations

1.1 tomorrow’s] del ink; ‘todays’ added ink
1.2 list from] ‘(alluded to in previous letter)’ interl ink
2.3 The observations … inch!! 2.4] scored ink
5.2 the same … seeds.] double underl ink

Footnotes

The year is established by the relationship between this letter and the letter from W. C. Marshall, 30 August [1874].
Marshall had sent leaves of Pinguicula (butterwort) on 30 August 1874 (see letter from W. C. Marshall, 30 August [1874]). CD had written that he would be interested in seeing a list Marshall was compiling, noting the number of insects found on Pinguicula leaves and the proportion of leaves with insects (letter to W. C. Marshall, [after 30 August 1874]). The list has not been found; see, however, Insectivorous plants, p. 370.
Parnassia palustris is marsh grass of Parnassus; Drosera rotundifolia is round-leaved or common sundew; Saxifraga aizoides is evergreen saxifrage; Anagallis tenella is bog pimpernel; Erica tetralix is the cross-leaved heath.
Only a draft of the letter to W. C. Marshall, [after 30 August 1874], has been found; it did not mention tracing the source of the sticky secretion.
CD suspected that Pinguicula could digest seeds as well as insects (see letter to W. T. Thiselton Dyer, 9 June 1874).
Horace Darwin was a friend of Marshall; the two were students at Trinity College, Cambridge, at the same time (Freeman 1978).

Summary

Sends Pinguicula vulgaris leaves with seeds on them, together with his observations on proportion of leaves with insects on them.

Letter details

Letter no.
DCP-LETT-9626
From
William Cecil (Bill) Marshall
To
Charles Robert Darwin
Sent from
Derwent Island
Source of text
DAR 58.1: 128–9
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 9626,” accessed on 20 August 2019, http://www.darwinproject.ac.uk/DCP-LETT-9626

Also published in The Correspondence of Charles Darwin, vol. 22

letter