intention, when I began this note, of running on at such length on hybridism; but you have been Objector-General on this head. LETTER 195. 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. As every one knows, in raising seedlings you may have every gradation from individuals identical with the parent, to slight varieties, to strongly marked varieties. Now, does this occur with buds or do only rather strongly marked varieties thus appear at rare intervals of time by buds? (195/2. Mr. Rivers could not give a decided answer, but he did not remember to have seen slight bud-variations. The question is discussed in "Variation under Domestication," Edition II., Volume I., page 443.) I should be most grateful for information. I may add that if you have observed in your enormous experience any remarkable "bud-variations," and could spare time to inform me, and allow me to quote them on your authority, it would be the greatest favour. I feel sure that these "bud-variations" are most interesting to any one endeavouring to make out what little can be made out on the obscure subject of variation. LETTER 196. TO T. RIVERS. Down, January 7th [1867?]. I thank you much for your letter and the parcel of shoots. The case of the yellow plum is a treasure, and is now safely recorded on your authority in its proper place, in contrast with A. Knight's case of the yellow magnum bonum sporting into red. (196/1. See "Variation under Domestication," Edition II., Volume I., page 399.) I could see no difference in the shoots, except that those of the yellow were thicker, and I presume that this is merely accidental: as you do not mention it, I further presume that there are no further differences in leaves or flowers of the two plums. I am very glad to hear about the yellow ash, and that you yourself have seen the jessamine case. I must confess that I hardly fully believed in it; but now I do, and very surprising it is.