My dear Henslow

I really can hardly enumerate how many things I have to thank you for.— There is all that you are doing for me in the seed line, (including the wild Carnation)¹ —the copies of the Hitcham List,² —your Programme & your note telling me how well your Fête³ seems to have turned out. The Horners have been staying here, & M^r Horner tells me he was once with one of your Excursions,⁴ & he was full of admiration at all the doings at Hitcham,—as indeed everyone must be.— Your Botanical little girls are simply marvellous; I am so glad to hear that you intend writing some little Book to show how to teach Botany:⁵ I find with my own children I hardly know how to begin.

I thank you much for attempting to mark the list of dubious species; I was afraid it was a very difficult task, from, as you say, the want of all definition of what a species is.— I think however you were marking exactly what I wanted to know. My wish was derived as follows: I have ascertained, that apparently (I will not take up time by showing how) there is more variation, a wider geographical range, & probably more individuals, in the species of large genera than in the species of small genera. These general facts seem to me very curious, & I wanted to ascertain one point more; viz whether the closely allied & dubious forms, which are generally considered as species, also belonged on average to large genera.—⁶

I sh^d. like sometime to know where you have recorded your opinion that a change in the character of one organ induces other changes; for curiously I have this summer been planting many varieties (46 Peas) chiefly for the sake of observing this very point.—⁷

Will you be so kind as to add specially to your list of desired seeds, the white Lychnis; for I have in vain endeavoured here to find the Plant.— Babington, I see, asserts that L. diurna & vespertina, differ (besides in colour) in form of capsule & in the teeth of the calyx. Gærtner further asserts that there is some difference in the period of their sleep, i.e., I suppose, closing their flowers: With all this, & as a guide to me to look out for the variable points, I sh^d. like, if you have any opportunity, to have the red & white Lychnis dried for me by your little girls.—⁸

I end this long note, by saying that I had intended coming to London before very long, & will come on 7^th or 8^th of August. But when it comes nearer the time, I will write & ask how I can have best chance of meeting you.

Ever your’s most truly | C. Darwin