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Darwin Correspondence Project

From Ludwig Molendo and Alexander Walther   5 August 1868


August 5th. 1868

Most honoured Sir!

It is a slight tribute paid by gratitude to instruction, when we send a trifling essay to the Reformator of Natural Philosophy, not without the hope that it may find a kind reception.

The inclosed book contains in its third part a slight investigation in your great theory, as far as we tried to apply its principles to the spreading about of the different species of moss.1

You yourself, most honoured Sir, have repeatedly encouraged to such investigations.

Until now no greater trial has, at least in Germany, been made to apply these principles to Kryptogames;2 and this one is also only a precursor; for Mr Molendo’s next work is devoted to the so-called law of migration, in which we do not see a new principle and, as to the long isolation—not one which is every where valid.3

We think that this first fruit of a branch of Botany, which until now was steril, may not be altogether unworthy of coming into your hands; as the study of your ideas has riprened it. But whether the fruit is indeed already ripe authors seldom know.

Also the Polygamic species were particularly taken into consideration and shall, in future, be subjected to more particular investigations.4 They seem to explain in a natural way certain cases of near affinity.

Our German Bryologians will, withhout doubt, attack this our way of considering the matter, and they are welcome to do so.

With the assurance of the highest consideration we are, most honoured Sir, yours very obedient servants | L. Molendo. | A. Walther


The book was Walther and Molendo 1868. There is a lightly annotated copy in the Darwin Library–CUL (see Marginalia 1: 843). The third part of the book (pp. 207–79) was headed ‘Pflanzengeographische Betrachtungen’ (phytogeographical considerations). In a note at the back of the book referring to page 224, CD wrote: ‘Even close species of moss do not live close together; the Struggle for Life, being severest between nearest forms—good!’
Kryptogames: i.e. cryptogams.
The ‘law of migration’ (Migrationgesetz) was developed by Moritz Wagner (Wagner 1868a and 1868b); his view was that a new species could appear only from a geographically isolated population of the parent species. Molendo’s work on the law of migration was apparently never published. See also Walther and Molendo 1868, pp. 263–5.
For the discussion of polygamic species in relation to natural selection, see Walther and Molendo 1868, pp. 272–7.


Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.


Send their work [Die Laubmoose Oberfrankens (1868)].

Letter details

Letter no.
Ludwig Molendo; Alexander Wilhelm Hannibal Franz (Alexander) Walther
Charles Robert Darwin
Sent from
Source of text
DAR 171: 229
Physical description
LS 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 6305,” accessed on 28 May 2024,

Also published in The Correspondence of Charles Darwin, vol. 16