It is mere virtue which makes me not wish to examine more orchids; for I like it far better than writing about varieties of cocks and hens and ducks. Nevertheless, I have just been looking at Lindley's list in the "Vegetable Kingdom," and I cannot resist one or two of his great division of Arethuseae, which includes Vanilla. And as I know so well the Ophreae, I should like (God forgive me) any one of the Satyriadae, Disidae and Corycidae. I fear my long lucubrations will have wearied you, but it has amused me to write, so forgive me. LETTER 601. TO J.D. HOOKER. (601/1. Part of the following letter is published in the "Life and Letters," the remainder, with the omission of part bearing on the Glen Roy problem, is now given as an example of the varied botanical assistance Darwin received from Sir Joseph Hooker. For the part relating to Verbascum see the "Variation of Animals and Plants," Edition II., 1875, Volume II., page 83. The point is that the white and yellow flowered plants which occur in two species of Verbascum are undoubted varieties, yet "the sterility which results from the crossing of the differently coloured varieties of the same species is fully as great as that which occurs in many cases when distinct species are crossed." The sterility of the long-styled form (B) of Linum grandiflorum, with its own pollen is described in "Forms of Flowers," Edition II., page 87: his conclusions on the short-styled form (A) differ from those in the present letter.) September 28th [1861]. I am going to beg for help, and I will explain why I want it. You offer Cypripedium; I should be very glad of a specimen, and of any good-sized Vandeae, or indeed any orchids, for this reason: I never thought of publishing separately, and therefore did not keep specimens in spirits, and now I should be very glad of a few woodcuts to illustrate my few remarks on exotic orchids. If you can send me any, send them by post in a tin canister on middle of day of Saturday, October 5th, for Sowerby will be here. Secondly: Have you any white and yellow varieties of Verbascum which you could give me, or propagate for me, or LEND me for a year? I have resolved to try Gartner's wonderful and repeated statement, that pollen of white and yellow varieties, whether used on the varieties or on DISTINCT species, has different potency. I do not think any experiment can be more important on the origin of species; for if he is correct we certainly have what Huxley calls new physiological species arising. I should require several species of Verbascum besides the white and yellow varieties of the same species. It will be tiresome work, but if I can anyhow get the plants, it shall be tried.