From Asa Gray   21 June 1858

Dear Darwin

A word more about self-fertilization in Fumariaceæ 1 After the tips of the outer pair of petals have separated or turned back, it is easy enough for your coadjutors the bees (whom I have never yet noticed about a Fumariaceæ) to push the cap of the inner petals to one side and reach the stigma; this is especially easy in Dicentra spectabilis & Adlumia: But in both these plants, also in Corydalis glauca & C. aurea, I generally find pollen on the stigma before the outer petals have opened, and before any insect can intermeddle. In Dicentra this is most sure, because the cup-shaped tips of the outer petals fit exactly against the sides of the crest of the inner ones, shutting all up completely until they turn back; but by this time the work is done, commonly in D. spectabilis, et,— In D. formosa or eximia if not then yet very soon afterwards. The shedding of the pollen & the opening of the outer petals is here about simultaneous, as far as I have observed.

So I must still think, that the arrangement in Fumariaceæ is intended to secure self-fertilization.

Excuse my hasty note, and believe me, as ever | Yours cordially | Asa Gray June 21st, 1858

CD annotations

Top of first page: ‘Ch. 3’brown crayon; ‘Crossing of Fumariaceae Kidney Beans—’ pencil
End of letter: ‘Aug 16th I have now seen B. hortense going to Corydalis lutea, & it was pretty to see how as it visited each flower it let off the trap. Apparently in consequence, Bee had unusual difficulty in withdrawing proboscis— Fresh flower of Adlumia cirrhosa bears nectar on both sides & hood moves equally well both ways & stigma pointed each side. Hooker has examined 2 other sp. of Corydalis & pistol sprang up— Dielytra eximia is name of red Fumariaceæ’2 pencil
1
Gray had claimed that Fumaria was a genus in which individuals perpetually self-fertilised, in contrast to CD’s view that all organic beings must occasionally cross-fertilise (see Correspondence vol. 6, letter from Asa Gray, 7 July 1857, and letter to Asa Gray, 29 November [1857]). CD investigated the subject experimentally in June 1858 (see n. 2, below).
2
The note forms part of CD’s record of observations made in May and June on the fertilisation of these and similar leguminous flowers by bees. The letter is bound with CD’s other slips and notes on the topic in DAR 76. See also letter to J. D. Hooker, 8 [June 1858]. Dielytra eximia is a synonym of Dicentra eximia, staggerweed.

Please cite as “DCP-LETT-2288,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-2288