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SUPRESSION OF THE POTATO DISEASE.

"Down, Beckenham, Kent, April 4th, 1876. [1]

"DEAR SIR, - I thank you for your very obliging letter, and present of the Essay and seeds.

"I cannot but think about the principle on which you are acting is right, and if you succeed you will have conferred an enormous benefit on the public. I am sorry that I was compelled to decline my answer being published, for I cannot to the present hour remember what I said.

"Dear Sir, yours faithfully,

"CH. DARWIN.

"J. Torbitt, Esq., Belfast."

[1] In Torbitt, James, Cras credemus. A treatise on the cultivation of the potato from the seed, having for proposed results the extinction of the disease, and a yield of thirty, forty or more tons of tubers per statute acre. Belfast: Alexander Mayne, F1978.

The following is the letter referred to above, and which I have obtained liberty to publish:-

"January 26th, 1876.

"MY DEAR SIR,- It is, I believe almost impossible to answer your question, what makes an individual; naturalists are generally agreed to look at all the members produced by one act of sexual generation as belonging to the same individual; but this definition will not apply to some of the lowest organisms, which multiply by self-division but not so far as is known by sexual generation.

How it is that a single cell or a very few cells suffice to give rise to a new organism will never be known until we can say what life is, and we are at present a long way off this goal. I wish I could have answered your question better. -

Dear Sir, yours faithfully,

"CH. DARWIN."

The principle on which I am acting is the cultivation of the plant from the seed; and the propagation by the act of those varieties only which do not become diseased. - J. T.

"April 14th, 1876. [2]

"MY DEAR SIR, - Professor Ansted's letter [3], which I return, is a very good one.

"The more I reflect on your scheme the more I believe it to be the one plan for succeeding in getting a sound variety.

"Hoping that you may be successful,

"I remain, my dear Sir,

"Yours faithfully, "CH. DARWIN.

"James Torbitt, Esq., Belfast.

[2] see Darwin, C. R. 1878. [Extracts of letters on potato cultivation.] In Torbitt, James, Cultivation of the Potato. To the Right Hon. Sir Stafford H. Northcote Bart., C.B., Chancellor of the Exchequer, &c., London. [Belfast: privately printed single sheet], F1979.

[3] David Thomas Ansted (1814-1880), geologist and writer. The said letter was published in Belfast News-Letter (22 April 1876), p. 2, see below.

Now, I entreat earnestly the landowners, to whom I have sent seed this season, to carefully consider the foregoing. It means to Ireland almost the whole difference between poverty and wealth. It means, at the least, twenty tons to the acre all sound, in place of, at the most, ten tons to the acre, one-half diseased. I may state that, among others, the Dukes of Abercorn, Bedford, and Sunderland are acting on my suggestions.

JAMES TORBITT, Belfast.

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"Athenenæum Club, London, 10th April, 1876. [4]

"DEAR SIR,

...."I have long felt, with you, that the continued repetition of the individual by buds, at least in plants which have the reproductive organs in different individuals, is a very undesirable thing.

...With regard to the potato and the vine, I can well imagine that the attacks of disease by fungoid growths are greatly facilitated by constitutional weakness, incident to a constant multiplication of tubers, cuttings, or grafts...

I have read your essay with great interest....

Natural selection of the strongest, by natural destruction of the weakest, is supported by experience and common sense....If I can help you with any experiments I shall be very glad....

"Yours very faithfully,

"D. T. Ansted."

"Down Beckenham, Kent,

April 14, 1876. [5]

"MY DEAR SIR - Professor Ansted's letter, which I return, is a very good one. The more I reflect on your scheme the more I believe it to be the one plan for succeeding in getting a sound variety. During the last ten years I have been experimenting on crossing plants, and shall publish the results in the autumn. The flowers of the genus solanum do not produce nectar, and are but little visited by insects, though I have seen some on the flowers of the potato. Nevertheless, they do not get inter-crossed so much as the flowers of most other plants; therefore I would strongly advise you to intercross any two varieties (and the more they differ in all respects the better) - that is, if you can get two varieties which are moderately free of the pest. I know that there is the strongest probability that seedlings raised from a cross of this kind would not only grow vigorously, but would possess greater constitutional vigour, so as to be less liable to disease of all kind and death. Hoping that you may be successful,

"I remain, my dear sir,

"Yours faithfully,

"CH. DARWIN.

"J. Torbitt, Esq., Belfast."

[4] Letter from David Thomas Ansted to James Torbitt, which Darwin enclosed in his reply to Torbitt.

[5] This letter was published in Correspondence vol. 24, pp. 166-7.