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Darwin Correspondence Project

From Friedrich Hildebrand   19 March 1877

Freiburg i/B.

March 19th 1877.

My dear Sir

I am realy very sorry that I cannot help you in the Oxalis Question.1 Though I remember, that I found several species of Oxalis in the Herbariums with cleistogamic flowers, I cannot tell you the names of them, for at that time, about 12 years ago, as I made my first observations on the Trimorphismus of Oxalis I thought that the cleistogamic flowers in this genus were sufficiently known, so I did not notice them. In my papers of that time I find only a notice that I saw three specimens of the trimorphic O. incarnata with cleistogamic flowers in the Herbarium of Seelmejer, that belongs to the: “Naturhistorischer Verein von Rheinland und Westphalen en Bonn”; but I think that they would not be of much use to you as you want living specimens.2

Regretting very much, that I cannot send you the desired Oxalis I remain,—dear Sir,—with much respect | yours | sincerely | Hildebrand

CD annotations

Top of letter: ‘Cleistogams’ red crayon


CD’s letter to Hildebrand has not been found. CD was working on cleistogamy and heterostyly in species of Oxalis (the genus of wood sorrels) for Forms of flowers. CD had probably asked Hildebrand whether he knew of species of Oxalis with cleistogamic flowers; see letter to J. D. Hooker, 20 March [1877] and n. 3.
Hildebrand’s earlier observations on Oxalis were published in Hildebrand 1866 and 1867; he discussed cleistogamy in Oxalis in Hildebrand 1867, pp. 74 and 78. In Forms of flowers, p. 322, CD cited Hildebrand 1866, p. 369, for Hildebrand’s observation that many species of Oxalis produced cleistogamic flowers, and remarked that he had heard from Hildebrand about O. incarnata (pale pink-sorrel or crimson wood sorrel) from the Cape of Good Hope. The Rheinische herbarium of the Naturhistorischer Verein der Rheinlande und Westfalens (Natural Historical Society of Rhineland and Westphalia) includes an important collection from Johann Friedrich Sehlmeyer (Naturhistorischer Verein der Rheinlande und Westfalens e. V., Das Rheinische Herbar,, accessed 20 November 2015).


Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.


Regrets he cannot help on Oxalis question. He did not note the names of species with cleistogamic flowers as he thought they were sufficiently known.

Letter details

Letter no.
Friedrich Hermann Gustav (Friedrich) Hildebrand
Charles Robert Darwin
Sent from
Source of text
DAR 111: A84
Physical description
2pp †

Please cite as

Darwin Correspondence Project, “Letter no. 10900,” accessed on 23 June 2021,