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Darwin Correspondence Project

To John Ralfs   13 July [1874]1

Down, | Beckenham, Kent.

July 13th

My dear Sir

Utricularia arrived in capital state, as my son tells me who took charge of the specimens & put them in water.— I was so unwell I could not leave the house.2 He worked all day at the bladders, & I can see that it will be most difficult to make out about the function of parts. But things may get brighter, for with all your great experience on Desmids under the microscope you must know well that one must have one’s brain clear & hand steady to do anything on difficult structures.3

With cordial thanks | Yours sincerely | Ch. Darwin

I shall be able to do nothing, I fear, today—


The year is established by the relationship between this letter and the letter from John Ralfs, 9 July 1874.
See letter from John Ralfs, 9 July 1874. Ralfs sent a small specimen of Utricularia (bladderwort). Francis Darwin was assisting CD with his experiments on Pinguicula (butterwort) and Utricularia. According to Emma Darwin’s diary (DAR 242), CD had a bad attack of diarrhoea and sickness on 13 July 1874.
Desmids (family Desmidiaceae) are freshwater single-cell green algae, noted for the wide variety of body shapes found in different species. Ralfs had written a monograph on the family, naming many new species (Ralfs 1848).


Ralfs, John. 1848. The British Desmidieæ. London: Reeve, Bentham, and Reeve.


Discusses specimens of Utricularia.

Mentions JR’s work on desmids [The British Desmidieae [Desmidiae!?] (1848)].

Letter details

Letter no.
Charles Robert Darwin
John Ralfs
Sent from
Source of text
American Philosophical Society (Mss.B.D25.443)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9546,” accessed on 1 December 2021,

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