To G. H. K. Thwaites   29 December [1862]

My dear M^r Thwaites

Can you give me any cases of what some gardeners call “Sports”, but what I shall call “bud-variations”, ie when a leaf-bud assumes suddenly a new character—like moss-rose on Provence &c.— I sh^d be very grateful for any authentic cases.—¹ Why I more particularly ask you, is that Sir R. Schomburghk says that at St Domingo, introduced flowers from the warmer temperate regions were there particularly apt to sport in this manner.²

I wrote some time ago to you about Cinchona being dimorphic like Primula;³ I have now better reason to believe that this is the case, & I I have proof that some of these dimorphic plants are absolutely sterile with their own-form pollen.—⁴

You mentioned two Ceylon genera (I have your note but names forgotten; one was allied to Menyanthes)⁵   Would you have kindness to examine them & see that both forms produce pollen & if you will, compare size of pollen. Or if you prefer could you send me the two forms of these genera in a letter, well dried, but not much pressed & named & then I could compare by soaking the pollen. The flowers sh^d not be old.⁶

I believe that you will forgive me for troubling you, & I remain | Yours very sincerely | Ch. Darwin

I am hard at work at a book on “Variation under Domestication”.⁷