In "The Life and Letters of Charles Darwin", Volume II, Darwin was writing in a letter:

With regard to the spread of a belief in the adaptation of flowers for cross-fertilisation, my father wrote to Mr. Bentham April 22, 1868:

"Most of the criticisms which I sometimes meet with in French works against the frequency of crossing, I am certain are the result of mere ignorance. I have never hitherto found the rule to fail that when an author describes the structure of a flower as specially adapted for self-fertilisation, it is really adapted for crossing. The Fumariaceae offer a good instance of this, and Treviranus threw this order in my teeth; but in Corydalis, Hildebrand shows how utterly false the idea of self-fertilisation is. This author's paper on Salvia is really worth reading, and I have observed some species, and know that he is accurate."

I found many meanings for "order", but I just can't find a suitable meaning for it in this context, and "Fumariaceae" is a subfamily, not an order!

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    I don't think it's the highly-specialised Linnaean taxonomy sense here. He's just referring to the "elegance, neatness, orderliness" of the rule he'd been applying to analyse self-flowering adaptations (that adaptations are actually optimised for hybrid crossing, not self-fertilisation). But it's very old text, with obscure phrasing. No-one would write like that today. Jan 4, 2022 at 12:35
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    I believe it’s a taxon, as in kingdom>phylum>class>**order**. That’s a guess though.
    – Dan Bron
    Jan 4, 2022 at 12:41

1 Answer 1


Botanical nomenclature is based on a hierarchy of ranks. Wikipedia gives a succinct summary of the hierarchy:


the order (Latin: ordo) is

a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. The well-known ranks in descending order are: life, domain, kingdom, phylum, class, order, family, genus, and species, with order fitting in between class and family. An order contains various plant families, each containing genera, each containing species.

enter image description here

Fumariaceae is a family of plants contained in the order Ranunculares

Families of Angiosperms


Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Ranunculiflorae; Ranunculales. Cronquist’s Subclass Magnoliidae; Papaverales. APG III core angiosperms; peripheral eudicot; Superorder Ranunculanae. APG IV Order Ranunculales.

Corydalis is a genus in the family Papaveraceae, in the order Ranunculales.


The Papaveraceae are an economically important family of about 42 genera and approximately 775 known species[3] of flowering plants in the order Ranunculales

Hence, Darwin is referring to controversy with Treviranus about the order Ranunculales, which contains his examples - of the family Fumariacae and the genus Corydalis (a member of family Papaveraceae).

Here is my attempt to summarize all this. Darwin had in mind the order Ranunculales, which contains the particular family and genus that he mentioned (both in red):

enter image description here

His mention of the genus Salvia (order Lamiaceae) is a more general comment that does not relate specifically to the order Ranunculales.

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