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Darwin Correspondence Project

To C. W. Crocker   1 June [1861]1

Down. | Bromley. | Kent. S.E.

June 1st.

My dear Sir

Pray do not in the least hurry yourself: any time will do for me, & I shall much value your information. I do not quite understand whether you are thinking of a general course of scientific experiments in crossing or only in relation to Hollyhocks.— I am pretty confident there is a fine open field for research in regard to crossing varieties which have been greatly neglected under a scientific point of view, though largely & loosely practised by gardeners. Species on the other have been largely experimented on. As you have lived so much abroad, German is probably quite familiar to you2 (I wish it were to me) & I would most strongly advise you to get Gärtners admirable “Versuche ueber die Bastardzeugung. 1849” & study it.—3 If ever you thought of taking up scientifically the subject of crossing & feel that you have indomitable patience, I would beg permission to make a few suggestions on experiments, which I would surely have tried, had time & health permitted.—

With hollyhocks, I think it would be very useful to ascertain the effects of crossing, especially of those varieties which commonly breed true. You probably know far better than I; but when I tried I castrated these flowers in bud, but I believe it would quite suffice to remove anthers before the stigmas expand; & then cover the flower with gauze or net.— It would be extremely interesting to test following point; impregnate a dozen flowers of, we will say, a yellow Hollyhock (if that kind breeds true) with a black or some widely different kind; & then fertilise 12 of the yellow flowers with pollen of yellow flowers from another plant, performing every manipulation the same to the two sets; & then observe whether any difference in number of seed, which ought to be Counted or weighed. This experiment wd. be very interesting on account of a wonderful statement on this head by Gärtner with respect to crossing white & yellow Verbascum.4

Are you a fancier of Pelargoniums? I could suggest some interesting experiments; but I must not run on.— Pray excuse me, & believe me— | My dear Sir | Yours very sincerely | C. Darwin


Dated by the relationship to the letter to the same unidentified correspondent, 18 May [1861].
Crocker spent some time as a gardener at the summer residence of Victoria, Princess Royal of Great Britain, near Berlin.
Gärtner 1849.
CD described Karl Friedrich von Gärtner’s experiments in crossing white and yellow varieties of Verbascum in Variation 2: 105–6. Gärtner asserted that crosses between differently coloured varieties, either of the same species or different species, produced less seed than crosses between similarly coloured varieties.


Suggests procedures for breeding experiments with hollyhocks. Recommends C. F. v. Gärtner [Bastarderzeugung (1849)]. [See also 3151]

Letter details

Letter no.
Charles Robert Darwin
Charles William Crocker
Sent from
Source of text
American Philosophical Society (251)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 3170,” accessed on 23 July 2019,

Also published in The Correspondence of Charles Darwin, vol. 9