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Darwin Correspondence Project

From James Torbitt   24 January 1876

Sydenham | Belfast

24th. Jan 1876

Charles Darwin Esqre. | Down | Beckenham | —Kent

My dear Sir

With profound respect—now that the course of the life of the Peronospora Infestans seems to have been fully traced out, I venture once again to address you and if what I have to say possesses no interest I can only rely on your goodness to pardon the intrusion.1

The matter is this— In the spring of 1873 I planted the cutting of a Vine, in the summer of 1874 it had put forth its adventitious roots and leaves. I then took it up, divided it longitudinally into two equal parts, cutting down exactly through the centre of the pith, and leaving to each half an equal quantity of roots and leaves. I planted it in separate pots and it continued to grow healthily until it was lost sight of—in the nursery gardens.2 That is for several months, until it had acquired increased bulk and was evidently capable of living.

And now my dear Sir what I would wish to be permitted to ask—if indeed a question on my part be admissible—and I need not seek to hide my opinion that in coming to you I come to the highest authority in the world on the subject—

What I wish to know is—what is this so divided plant? is it an individual or several? Have both parts received an accession to the original stock of life, or only one of the parts? Or have neither? If neither, then how can dividing a plant into unequal parts, and calling one the stem and the other the scion be supposed to effect a new birth—afford a new starting point of life? May not after all the sexual union be the only rejuvenator of life? The true and only starting point of the life of the individual?3

I venture to forward herewith some matter in type,4 in the hope that it may be considered not unworthy of perusal and have the honour to be my dear Sir | most respectfully yours | James Torbitt


Peronospora infestans (now Phytophthora infestans), is a parasitic water mould responsible for causing potato late blight. The cycle of infection had been demonstrated by Anton de Bary in the 1860s (DSB). No previous letter from Torbitt has been found.
This account is taken almost verbatim from Torbitt’s paper ‘Potato cultivation’ (Torbitt 1875, p. 121). Torbitt believed that propagation by division had lowered the potato’s resistance to late blight and proposed raising it instead from seed. Torbitt 1875 was published in the Proceedings of the Belfast Natural History and Philosophical Society.
Torbitt had posed the same questions in his published account of the experiment (Torbitt 1875, p. 122).
No copy of Torbitt 1875 has been found in the Darwin Archive–CUL.


DSB: Dictionary of scientific biography. Edited by Charles Coulston Gillispie and Frederic L. Holmes. 18 vols. including index and supplements. New York: Charles Scribner’s Sons. 1970–90.

Torbitt, James. 1875. Potato cultivation. [Read 14 April 1875.] Proceedings of the Belfast Natural History and Philosophical Society (1874–5): 112–25.


Are plants that arise from vegetative propagation individuals or merely parts of the original parent plant?

Letter details

Letter no.
James Torbitt
Charles Robert Darwin
Sent from
Source of text
DAR 178: 130
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 10365,” accessed on 22 January 2022,

Also published in The Correspondence of Charles Darwin, vol. 24