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Darwin Correspondence Project

From W. T. Thiselton-Dyer   [after 20 October 1873?]1

Royal Gardens Kew

The residue left on evaporation of the fluid in Nepenthes consists, if we take the average of these determinations at 31.61% of

Malic & a little citric acid 38.61
Chloride of Potassium 50.42
Soda 6.36
Lime 2.59
Magnesia 2.59

Voelcker in Ann & Mag. Nat. Hist 1849. IV. p. 1352

CD annotations

1.1 Nepenthes] underl red crayon
2.1 Voelcker … 135] double scored red crayon


The date is conjectured from the relationship between this letter and the letter from J. D. Hooker, 20 October 1873.
Thiselton-Dyer’s quotation is from Augustus Voelcker in Voelcker 1849. The original text in fact reads, ‘The unburnt residue left on evaporation of the fluid in the ascidia of Nepenthes therefore consists, if we take the average of the loss of the three determinations at 31.61 per cent. and reject the carbonic acid of the ash, of— Organic matter, chiefly Malic acid …’ See letter from J. D. Hooker, 20 October 1873. CD was interested in the chemical composition of the fluid in the pitchers of Nepenthes (the tropical pitcher-plant; see Insectivorous plants, p. 97).


Composition of the residue left on evaporation of the fluid in Nepenthes.

Letter details

Letter no.
William Turner Thiselton-Dyer
Charles Robert Darwin
Sent from
Source of text
DAR 60.2: 58
Physical description
Amem 1p

Please cite as

Darwin Correspondence Project, “Letter no. 9792,” accessed on 16 July 2019,

Also published in The Correspondence of Charles Darwin, vol. 21