TO T.RIVERS.
(195/1.

For another letter of Mr.Darwin's to him see "Life and Letters," III., page 57.) Down, December 23rd [1866 ?].
I do not know whether you will forgive a stranger addressing you.
My name may possibly be known to you.

I am now writing a book on the variation of animals and plants under domestication; and there is one little piece of information which it is more likely that you could give me than any man in the world, if you can spare half an hour from your professional labours, and are inclined to be so kind.

I am collecting all accounts of what some call "sports," that is, of what I shall call "bud-variations," i.e.a moss-rose suddenly appearing on a Provence rose--a nectarine on a peach, etc.

Now, what I want to know, and which is not likely to be recorded in print, is whether very slight differences, too slight to be worth propagating, thus appear suddenly by buds.