DURATION OF VARIETIES OF PLANTS 



being sound at heart, if I may so speak, will, ovA'ing to their inherent strength be restored 

 to better health, exactly as in the case of animals in the prime of life laboring under local 

 or transitory circumstances affecting their health. But we may graft a scion of an old 

 nearly worn out variety on a healthy j'oung stock, we may jilant it in a situation where 

 trees of the same variety continued, previously, in health and vigor upwards of a hundred 

 years and where younger varieties now grow healthy and vigorously, but *' the young 

 stock," as Mr. Knight observed, " can give nutriment only, not new life;" it is found 

 therefore, that the feeble scion, like a weak seedling, soon shows sj'mptoms of disease. 

 If it be objected that external influences first caused the feebleness, this may be said as 

 reasonably of the infirmities of age in animals. It is inherent weakness in both which 

 renders the attack of ordinary external influences formidable. 



When a variety of apple or potato has arrived at the best and most productive period 

 of its existence, is it rational to suppose or expect that the ingenuity of man can keep it 

 stationary'' forever, and prevent its decline? The inherent, and many of the external in- 

 fluences which lead to debility and death, are beyond the control of man; and every ad- 

 verse influence to which plants or animals are exposed, contributes more or less, to pros- 

 trate and wear out the constitution; and the power of external influences increases in pro- 

 portion to the diminution of vital power. Man, by various expedients, may postpone the 

 evil day, but he cannot prevent its coming. He may, for instance, betake himself to Italy 

 or Madeira, in order to bolster up his feeble constitution, and he may take plants of his 

 favorite old invalid fruit trees, with him, as a warmer climate is found to be as beneficial 

 to them as to him, and both may return to their native land considerably fortified, but 

 certainly not restored to the vigor of youth. 



Proofs of the degeneracy of varieties of the potato, are too numerous to admit of doubt. 

 The changes induced in a variety by time, are, I believe, very accurately described by the 

 editor of the Irish Farmer's Magazine.* " In a few years," he observes " after a variety 

 has been raised from seed, it arrives at its greatest degree of productiveness; then it con- 

 tinues annually, for a number of years, to decrease in productiveness, but to become more 

 valuable for food, being more farinaceous, or as it is termed, drier; afterwards it begins to 

 lose this quality, also, and rapid^' to decline, until in a few years more, it is utterly use- 

 less." Dr. LiNDLEY offers an explanation of these facts also, which he wishes us to substi- 

 tute for that of Mr. Knight; " a potato forced in such land," he observes, " has a fee- 

 ble constitution, and a small matter makes it ill; its unhealthiness is communicated to its 

 successors, and so the evil is ceaselessly augmented." He further remarks, " after six 

 months unnatural treatment during winter, the tubers are committed to the ground, and 

 though we have no reason whatever, to connect this practice with the blight, it is impossi- 

 ble to doubt that such a practice, long persevered in, must have a tendency to diminish 

 the constitutional vigor of the crop." The remedy proposed is to raise potatoes for sets 

 upon a different principle from those which are for the table; they must be grown in poor, 

 light land, left in the ground undug during winter, or planted in autumn, or if taken up 

 and not planted in autumn, they must be thoroughl}' greened and packed in sand, ^nd 

 we are to comfort ourselves with the belief that these means are sufficient to restore the 

 potato to its primitive vigor, and that it is nonsense to think of troubling ourselves by rais- 

 ing new varieties from seed. 



Can it be considered probable, that this method of renovating the health of aged or dis- 

 eased varieties of the potato, should have escaped the attention of Mr. Knight. He knew 

 the pernicious efi'ects on the progeny of over-feeding our domestic cattle, with a view 



* 1S34, p. 340 



