Ɛpsilon

To J. J. Weir   10 July 1875

Down, Beckenham, Kent

July 10 1875

My dear Sir

I do not know how to thank you enough; pray give also my thanks and kind remembrances to your brother.1 I am sure you will forgive my expressing my doubts freely, as I well know that you desire the truth more than anything else. I cannot avoid the belief that some nurseryman has sold C. adami to your brother in place of the true C. purpureus.2 The latter is a little bush only 3 ft. high (Loudon),3 and when I read your account, it seemed to me a physical impossibility that a sporting branch of C. alpinus could grow to any size and be supported on the extremely delicate branches of C. purpureus. If I understand rightly your letter, you consider the tuft of small shoots on one side of the sporting C. alpinus from Weirleigh as C. purpureus; but these shoots are certainly those of C. adami. I earnestly beg you to look at the specimens enclosed. The branch of the true C. purpureus is the largest which I could find. If C. adami was sold to your brother as C. purpureus, everything is explained; for then the gardener has grafted C. adami on C. alpinus, and the former has sported in the usual manner; but has not sported into C. purpureus, only into C. alpinus. C. adami does sport less frequently into C. purpureus than into C. alpinus. Are the purple flowers borne on moderately long racemes? If so, the plant is certainly C. adami, for the true C. purpureus bears flowers close to the branches. I am very sorry to be so troublesome, but I am very anxious to hear again from you.

My dear Sir | Yours very sincerely | Charles Darwin

C. purpureus bears “flowers axillary, solitary, stalked.”4

⁠⟨⁠P⁠⟩⁠.S I think you said that the purple at Weirleigh does not seed, whereas the pure C. purpureus seeds freely, as you may see in enclosed.

C. adami never produces seeds or pods

AL and Copy5

2
Weir had described sporting branches on what he presumed to be a graft of Cytisus purpureus (purple broom) onto the yellow-flowered C. alpinus (now Laburnum alpinum, Scotch laburnum; see letter from J. J. Weir, 9 July 1875). Cytisus adami is a graft hybrid of the common yellow laburnum, C. laburnum (now Laburnum anagyroides), and C. purpureus; its branches commonly revert to the parent species, bearing either yellow or purple flowers (see letter to J. J. Weir, 5 July 1875 and n. 3). Cytisus adami is now known as +Laburnocytisus adamii. In Variation 2d ed. 1: 417 n. 99, CD added a note about cases in which C. adami had been sold in place of C. purpureus.
3
Cytisus purpureus (a synonym of Chamaecytisus purpureus, purple broom) is described in John Claudius Loudon’s Encyclopædia of plants (Loudon 1841, pp. 624–5).
4
Loudon 1841, p. 625.
5
The letter down to ‘solitary, stalked’ is transcribed from a copy in DAR 148: 336; the postscript was written by CD on the back of the envelope, which is now at the American Philosophical Society.

Please cite as “DCP-LETT-10056,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10056