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Darwin Correspondence Project

From Friedrich Hildebrand   2 January 1868


January 2nd | 1868.

Dear and honoured Sir!

I am very much obliged to you for sending me a german copy of your last work on the Domestication of animals and plants.1 You will not expect me to make you a series of elogies, for I may suppose that you have seen from my writings how very much I estimate all your works.2 Allow me only a few remarks that very likely will be of interest for you.

Firstly I have raised last summer two hybrid-knolls of potatoes by grafting. I took potatoes that were white and had a smooth skin, and such that were red and scaly. From both varieties I cut out all the eyes and put in their places eyes from the red potatoes in the white and eyes from the white in the red knolls. Though most of these potatoes did not grow I got from them two bushes producing two knolls, besides others, that held the middle between the red and white potatoes: they were red and scaly at the one end, white and smooth at the other and in the middle smooth and white with red stripes. In the knoll produced from a red eye the red colour was prevailing, in that from a white eye, the white. This result astonished me very much and I am now, with you, inclined to believe that Cytisus Adami is a graft-hybrid (I do not know if this is your english word) too. I intend to make more experiments about this interesting matter.3

Secondly, as I intended to write an essay on the direct influence of the pollen on the fruit produced by its fecundation, I experimentized with plants of yellow and red Mays, without knowing that anybody had done it before; and had the same results as Dr Savi, by crossing a yellow variety with the pollen of a red one, I got two bushels the corns of which were either yellow or brownish-violet, in a third bushel not the seeds but the axis had got a brownish colour.4

Finally I have found on a Herbst Caleville appel-tree—the Herbst Caleville have a yellow colour with red dots, never stripes—growing on a branch that was stretched out between the branches of a red Caleville, an apple, that had a large red stripe on one side, of the red Caleville’s colour, and under this stripe the vascular bundels were red, as it is so characteristic for the red Caleville. I am persuaded that this apple was produced by the pollen of the red Caleville acting on the ovarium of a Herbst Caleville’s flower. On another apple-tree, the apples of which are yellow, with red dots, and very short stripes, I have observed every year on a branch interlaced with the branches of a red Stettiner, appels that were either yellow with several red stripes from top to toe, or quite red but lighter as the Stettiner.—5

By your work it has become unnecessary, at least for some time to write a longer essay about the graft-hybrids and the direct influence of the pollen, so I shall give up my intention and only publish the notices, I have given you.—6 Signore Delpino asked me for your address and will have send you his writings. I think he has rather misunderstood you in some way, but he is, as you will have seen an accurate observer.7

Wishing you a happy new-year I remain, | Dear Sir | yours | respectfully | Hildebrand


The reference is to the German translation of Variation (Carus trans. 1868). CD evidently had arranged for Hildebrand to be sent a copy of the first volume (see letter to Friedrich Hildebrand, 5 January [1868]). Hildebrand’s name appears on the presentation list for the book (see Correspondence vol. 16, Appendix IV).
On Hildebrand’s support for CD’s work see, for example, Hildebrand 1865b, Correspondence vol. 14, letter from Friedrich Hildebrand, 24 July 1866, and Correspondence vol. 15, letter from Friedrich Hildebrand, 18 March 1867. Copies of many of Hildebrand’s papers are in the Darwin Pamphlet Collection–CUL.
CD added the information from Hildebrand’s letter to the second printing of Variation, which appeared in February 1868 (Variation 1: 396). CD had earlier been interested in experiments by Robert Trail in which two differently coloured potato varieties were grafted, producing some tubers that were mottled. CD remarked that the experiments showed ‘clear evidence of the intimate commingling of the two varieties’ (see Variation 1: 395–6, and Correspondence vol. 15, letter from Robert Trail, 5 April 1867). CD described similar characteristics in Cytisus adami (now +Laburnocytisus adamii), whose origin as a graft hybrid was disputed at the time (see Variation 1: 387–97). CD argued that the production of graft hybrids could be explained by his hypothesis of pangenesis (Variation 2: 364–5).
CD cited Hildebrand’s experiments on yellow and red maize, together with those of Gaetano Savi, in his discussion of the ‘direct action of the male element on the mother form’, in the second printing of Variation (Variation 1: 400 and n. 126).
CD added a reference to Hildebrand’s observations of apple varieties in the second printing of Variation (Variation 1: 400, n. 126).
Hildebrand’s observations and the results of his experiments on potatoes, maize, and apples were published in the 15 May 1868 issue of Botanische Zeitung (Hildebrand 1868a).
Federico Delpino had sent CD several papers in 1867, and had given qualified praise of CD’s work in his letter of 5 September 1867 (Correspondence vol. 15). For more on Delpino’s views of CD’s theory, see Pancaldi 1984.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Reports making graft-hybrid potatoes.

Has found direct action of pollen in Mays [Zea] crosses and apple-trees.

F. Delpino has asked for CD’s address.

Letter details

Letter no.
Friedrich Hermann Gustav (Friedrich) Hildebrand
Charles Robert Darwin
Sent from
Source of text
DAR 166: 207
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 5774,” accessed on 25 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 16