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Darwin Correspondence Project

To Francis Darwin   [22 November 1878]

[4 Bryanston Street, London.]

My dear Backy

It is grand about the Pelargonium leaves & seems to me a most curious subject to investigate.1 I think that I will endeavour to see Frankland & see what he can suggest.2 It seems to me that you ought now to ascertain whether any alkali comes from leaves without glands or Hairs, & secondly whether the elimination is connected with the action of light, excluding every ray.3

If you can decide anything before we go let me hear. If I see Frankland, it will be on Monday or Tuesday. Boussingault4 statement that salts pass into leaves has some bearing with your discovery that they pass out of leaves.— With plants not exposed to rain & not syringed out, there ought to be potash on the surface, so that if many leaves were rapidly washed & the water evaporated almost to dryness, these ought to be alkaline. Can the good of syringing be in part to wash off the excreted matter?5

Have another go with radicles of Horse-chesnut— These are far more important than Spanish chesnut for me.—6 In the study there is basket with Horse-chesnuts put all of them to soak for 36o & then put onto tin-boxes in Hot-House for germination.—

Tell abbadubba7 that Baba sends him a kiss.

yours affect | C. D


Francis had described experiments with geranium leaves in his letter of [before 22 November 1878]; geranium is sometimes used as a common name for both Geranium and Pelargonium.
Leaves of Geranium and Pelargonium have trichomes (hairs); CD may have wanted to eliminate the possibility that the dissolved matter was secreted from the trichomes rather than the pores of the leaf.
Jean-Baptiste Boussingault.
While in Würzburg, Francis had conducted experiments on whether bloom prevented nitrogenous matter in leaves from expiring when the leaf was immersed in water (see letter from Francis Darwin, [4–7 August 1878] and nn. 4 and 8).


Suggests experiment to detect salts deposited on surface of leaves.

Wants FD to have another go at horse-chestnut radicles.

Letter details

Letter no.
Charles Robert Darwin
Francis Darwin
Sent from
London, Bryanston St, 4
NO 22 78
Source of text
DAR 211: 48
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 11755,” accessed on 30 May 2023,