From W. T. Thiselton-Dyer   [20 January 1879]1

the species of Oxalis.

O. tropæoloides = O. corniculata, L. var. atropurpurea

It is nothing more than a form of the well known O. corniculata with Copper coloured foliage2

The Cactus is no doubt a merely trifling variety of Pilocereus Houlletii3

Apropos of our conversation on means of geographical distribution I think you would be interested at glancing at what Moseley says in the 15th. volume of the Journal of the Linnean Society p. 77 about pigeons ejecting seeds in a fit state for germination.4 He apparently regards this as the most efficient means of transport for all but littoral species in the Malayan archipelago.

One does not like to venture to propose any particular undertaking to you as you must know so much better than any one else what is most important to be done, but your collected notes on geographical distribution wd. form a most delightful book5

incomplete

CD annotations

1.1 the species … foliage 3.2] crossed pencil
4.1 The Cactus … Houlletii] crossed ink
5.1 Apropos … Moseley 5.2] crossed pencil
5.2 says] after ‘Moseley’ interl pencil
6.1 One does … book 6.4] crossed pencil
Top of second page: ‘Geograph. Distribution’ pencil
1
The date is established by a note attached to the letter to W. T. Thiselton-Dyer, 25 January [1879]. This note contained a list of queries for Thiselton-Dyer, most of which CD crossed out as having been dealt with either in his letter or in Thiselton-Dyer’s preceding letter. Thiselton-Dyer annotated one of them, ‘Seeds of Drosophyllum’, ‘Ansd Jany. 20/79’. From CD’s letter to Thiselton-Dyer of 25 January [1879], it is evident that Thiselton-Dyer discussed Drosophyllum in a missing part of this letter.
2
Oxalis tropaeoloides is a synonym of the horticultural variety O. corniculata var. atropurpurea. In Movement in plants, p. 118, CD referred to seedlings purchased under the name O. tropaeoloides, but ‘certainly belonging’ to the variety O. corniculata var. atropurpurea.
3
Pilocereus houlletii is an unresolved name; Pilocereus houlettii is a synonym of Cereus houlletii. CD mentioned Pilocereus houlletii in Movement in plants, p. 97.
4
Henry Nottidge Moseley was writing about the Admiralty Islands, which are north of New Guinea, not in the Malay Archipelago (Moseley 1875a). Thiselton-Dyer visited Down on 18 January 1879 (Emma Darwin’s diary (DAR 242)).
5
CD’s unpublished notes on geographical distribution are in DAR 205.4; for his published research, see Origin 6th ed., chapters 12 and 13.

Please cite as “DCP-LETT-10341,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10341