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Darwin Correspondence Project

From Daniel Oliver   27 November 1863

Royal Gardens Kew

27. Nov. 1863

My dear Sir

It was very kind of you to trouble to send the reference to Wyman’s paper.1 I understood it was in Boston Journal.2 I must look it up next time I go in to the Societies.3

The hygroscopic bundles in pods of Pentaclethra undergo wonderful amount of extension when moistened—increasing about 16 per Cent. It is curious that this extension is in direction of the length of the cells of the contracting & expanding tissue. In Common Pea, Lathyrus &c. the contraction on drying—causing curling up of valves is in direction of breadth of the cells. In wood the principal contraction is also transverse.4 It is curious to cut with scissors the strips marked from pod of sweet Pea dry, & put one of them in water a few minutes & 〈then〉 compare.


The directio〈n of〉 cells of contracting 〈tissue〉 is indicated on inner 〈surface〉 of the valves 〈by the〉 fine striation. The p〈ods〉 shd. be cut to equal le〈ngth〉5

I see v. Mohl is wr〈iting〉 in Bot. Zeit. on the s〈mall〉 hermetic flowers of Oxalis〉 〈    〉6

He has made more 〈    〉 obs. than we previously 〈    〉 but seems to attach u〈ndue〉 importance to the phen〈omenon〉7

If there were any p〈ods〉 with these flowers only 〈    〉 might be ground for such.

However he makes out that Fumaria is necessarily a self-fertilizing plant & makes a little flourish about it which by the way I think you have made some observations wh. may enable you to refute him.8

I forget whether you said you had actually found bees carrying pollen of Fumitories.9 But it is too bad of me troubling you about things while so poorly.

Very sincerely yours | Danl. Oliver

I tho’t of noticing Mohl in N.H.R. & would refer to yr. obs. on Fumitory if worth while?10

CD annotations

1.1 It was … equal le〈ngth〉 2.10] crossed pencil


See letter to Daniel Oliver, [before 27 November 1863]. Oliver’s interest in Wyman 1854 was related to a paper he read on the mode of dehiscence of the pods of Pentaclethra macrophylla, a legume from Fernando Po, before the Linnean Society of London on 19 November 1863 (Oliver 1863e).
In the letter to J. D. Hooker, [22–3 November 1863], CD stated that Wyman 1854 had been published in the Proceedings of the Boston Society of Natural History rather than in the Proceedings of the American Academy of Arts and Sciences.
Oliver was a fellow of both the Linnean Society and the Royal Society (R. Desmond 1994).
Oliver wrote this sentence in the left hand margin of the second page of the letter.
Oliver described this experiment on Lathyrus in Oliver 1863e, p. 419.
Hugo von Mohl discussed Oxalis acetosella in Mohl 1863, pp. 321–2, 326, 327. There is an annotated copy of Mohl 1863 in the Darwin Pamphlet Collection–CUL.
In [Oliver] 1864b, pp. 243–4 (see n. 10, below), Oliver noted the observations that Mohl 1863 had added to what was already known of the small, unopening flowers (later called cleistogamic); Oliver referred back to his own discussion ([Oliver] 1862b, pp. 238–43) of Oxalis acetosella and several other plants bearing cleistogamic flowers. In reviewing Mohl’s discussion of the unopening flowers, Oliver wrote ([Oliver] 1864b, pp. 245–6) that Mohl: ascribes an undue importance to them, especially when he proceeds to couple with them the self-fertilising homomorphic flowers … and opposes them collectively to the alleged ‘law of nature,’ that both in the vegetable and animal kingdoms** there shall be an occasional intercross of distinct individuals. Oliver’s asterisk referred to Origin, p. 101, where CD stated that ‘both in the vegetable and animal kingdoms, an occasional intercross with a distinct individual is a law of nature’.
Mohl referred to the family Fumariaceae as necessarily self-fertilising, without specifying the genus Fumaria (Mohl 1863, p. 325). He believed that Fumariaceae provided a counter-example to CD’s statement in Orchids, p. 359: ‘Nature thus tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation’. CD had observed insects pollinating other genera of Fumariaceae but had never observed pollination of Fumaria; however, the structure of the Fumaria flowers convinced him that they were occasionally pollinated by diurnal insects (see Correspondence vol. 9, letter to Daniel Oliver, 9 April [1861], Correspondence vol. 10, letter to Daniel Oliver, 12 [April 1862], and Cross and self fertilisation, p. 366; see also letter to Nature, 6 April 1874 (Calendar no. 9393, Collected papers 2: 182–3)). CD’s botanical notes on Fumariaceae, dated from 1857 to 1863, are in DAR 76: B13–21.
CD had observed bees inside flowers of a plant that he had thought was Fumaria but that Oliver later identified as Corydalis (also a member of the Fumariaceae) (see Correspondence vol. 9, letter to Daniel Oliver, 9 April [1861] and DAR 76: B17).
A review by Oliver of Mohl 1863 and seven other works on dimorphic flowers also published in 1863 appeared in the April 1864 issue of the Natural History Review ([Oliver] 1864b; see also n. 7, above). A note ([Oliver] 1864b, p. 243 n.) stated that the papers reviewed were ‘suggested by the researches of Mr. Darwin’. See also n. 8, above, and Correspondence vol. 12, letter to J. D. Hooker, 5 April [1864].


Discusses the contraction of hygroscopic bundles in seed-pods,

and a paper by Hugo von Mohl ["Über dimorphe Blüthen", Bot. Ztg. (1863): 309–15, 321–8] in which he discusses Oxalis and determines that Fumaria is a necessarily self-fertilising plant.

Letter details

Letter no.
Daniel Oliver
Charles Robert Darwin
Sent from
Source of text
DAR 173: 24
Physical description
4pp inc †

Please cite as

Darwin Correspondence Project, “Letter no. 4349,” accessed on 22 January 2018,

Also published in The Correspondence of Charles Darwin, vol. 11