TREATISE
ON
THE CULTIVATION OF THE POTATO.
At the Meeting of the British Association at Belfast in the summer of 1874, I stated my opinion, that the sexual combination resulting in the birth of the seed, formed the true and only starting point of the life of the individual; that plants propagated by their buds were yearly growing older, and that the process of cutting them to pieces and planting them in the earth could not, therefore, be carried out for ever. And I illustrated my statement by the following experiment. In the spring of 1873, I planted the cutting of a Vine; in the spring 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 exhibited it growing healthily to the Biological Section of the Association. I argued that it was only one individual, as regards the duration of life; that neither half had received any accession to its original stock of life—obtained a new birth or new starting point of life—and that if cutting a plant into two equal parts did not effect a new birth, neither could cutting it into two unequal parts, and calling one the stem and the other the scion, do so. I pointed out that the potato, when propagated by the "set" for a series of years, undergoes a change; that in the season of its bloom, here and there a pedicel breaks at its junction with the calyx, the flower drops off, and a berry, which should have contained from seventy-five to a hundred seeds, is wanting in that cluster; that when so propagated for a further series of years, all the pedicels break, and the plant becomes utterly sterile, the condition to which the Skerry Blue is now reduced; that when so propagated for another series of years, it becomes unable to re-
