To J. S. Henslow   21 July [1855]

Down Farnborough Kent

July 21st

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, & Mr 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 shd. 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 shd. 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 7th or 8th 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

1
Dianthus caryophyllus. CD had requested seeds for a hybridising experiment. See letter to J. S. Henslow, 11 July [1855].
2
Henslow 1855a, marked to show close species.
3
Henslow held agricultural shows twice a year at which the local farm labourers could exhibit their produce and compete for prizes. The occasions also included lectures and exhibits designed to encourage improvements in cultivation. See Russell-Gebbett 1977, pp. 77–81; the July 1855 f|fs5fs5|ête is mentioned on p. 81.
4
Henslow’s ‘village excursions’ were described in the Gardeners’ Chronicle and Agricultural Gazette in 1850. Excerpts from Henslow’s invitations and regulations for some of the expeditions are printed in Russell-Gebbett 1977, pp. 84–7.
5
Henslow contributed fourteen ‘Practical lessons in botany for beginners of all classes’ to the Gardeners’ Chronicle and Agricultural Gazette in 1856. His projected book, however, was left unfinished at his death (L. Huxley ed. 1918, 1: 391).
6
See letter to J. S. Henslow, 14 July [1855]. A description of CD’s belief that closely allied species are more likely to be found in genera that also have a large number of varieties is in Natural selection, pp. 134–64, especially 147–8. See also Browne 1980.
7
CD discussed the ‘correlation of growth’ in Natural selection, pp. 297–304, and in Origin, pp. 143–50. Henslow did not publish this opinion explicitly, but it was implied in his practical researches carried out on variation and monstrosities of flowers, particularly in Henslow 1832.

Manuscript Alterations and Comments

0.2 21st] over ‘20th’; before del ‘19th’
1.2 (including the wild Carnation) 1.3] interl
1.4 telling] ‘t’ over illeg
1.6 at] ‘a’ over ‘w’
1.8 Botany] interl
2.3 however] interl
2.4 (I will … showing how) 2.5] interl
2.6 & probably] ‘&’ interl
2.7 viz] interl
2.7 closely] altered from ‘close’
2.8 generally] after del ‘probably’
2.8 on average] interl
3.3 this summer] after del ‘just’
4.2 Babington] after del ‘And’
4.3 in colour] ‘in’ interl
5.2 when] after del ‘b’

Please cite as “DCP-LETT-1726,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-1726