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 continues 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 rapidly to decline, until in a few years more, it is utterly useless." Dr. Lindley offers an explanation of these facts also, which he wishes us to substitute for that of Mr. Knight; "a potato forced in such land," he observes, "has a feeble 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 impossible 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, to premiums, as one of my letters from him testifies, and doubtless no man was better aware of the injurious effects of an excess of food and other influences on plants.

Then consider the attention which he obviously paid to the culture of the potato, the unusual care and diligence with which he conducted all his inquiries, and the anxious desire he ever manifested to arrive at the truth, by repeatedly trying experiments from which he suspected results unfavorable to the conclusions at which he had arrived. The object, moreover, which he constantly had in view, was utility. To be useful to his country and fellow men, by discovering important truths in cultivation, was the aim of all his inquiries. Yet, with such qualifications as these, and when near the close of his invaluable labors, and after fifty years, at least, of experiments and observations on plants, Mr. Knight said, "I have, in several instances, tried to renovate the vigor of old and excellent nearly expended varieties of the potato, by change of soil and mode of culture, but I never in any degree, succeeded; all became unproductive and worthless." Yet, notwithstanding, Mr. Knight, with his profound knowledge of the laws of vegetable life, and his great skill as a cultivator, was foiled in his repeated endeavors to re-invigorate old varieties of the potato; the peasantry of England were seriously told, that to think of renovating the potato crop, by raising new varieties from seed, was a dream, and that if they would only adopt certain methods, they might restore old varieties to health and vigor, and so continue them healthy and vigorous forever.

The failure of Mr. Knight and others, to restore old varieties of the potato to health, is not the only ground for doubting the efficacy of the means recommended by Dr. Lind-let. If the feebleness of the constitution, or the wearing out of varieties were a consequence chiefly of their being grown in too rich land, or frequently repeated on the same land, surely garden varieties should have been short lived, and most subject to disease, for gardens generally are much more highly manured than fields, and there the crop is most frequently repeated. But early varieties seem upon the whole, to have been more free from disease than late, or field varieties, and I am inclined to believe that as a general rule, they continue in a healthy and useful condition for a much greater length of time, owing to the non-production of blossoms and seeds. These do not, moreover, have the same high farming in other countries as in England, of late years; and in England, what may be called high farming, is even now the exception, and not the rule.

Much of the arable land in the first settled parts of the United States, is well known to have been considerably exhausted by taking repeated white crops, without making any adequate return to the soil, in the shape of manure, yet the blight of the potato has been fully as virulent in the United States as in England. In this section of the country, the potato has been grown on land first broken up two or three years ago, and to which, in many instances, no manure has been applied, but the crops are blighted, our plants are now nearly destitute of foliage, and in many cases a very considerable proportion of the tubers has already decayed.

Varieties of the ranunculus and anemone, which are propagated by their tubers, are also exempt from many of the causes which Dr. Lindley says must be avoided in the future cultivation of the potato, with a view to restore it to health. The tubers of these plants are not gathered into heaps, and suffered to heat during winter; they are not allowed to grow before planting in spring; consequently no useless sprouts are rubbed off; they are not planted on raw manure, nor are they cut into sets; therefore there is no loss of sap, or danger of injury from external causes arising from that practice. Yet, notwithstanding these disadvantages, and notwithstanding the care and skill bestowed upon them by the ardent florists, varieties of these plants unquestionably degenerate and wear out.

One of the first authorities on the ranunculus, the Rev. Mr. Tyso, a gentleman who has raised thousands of this beautiful flower from seeds, observes that "the longevity of the ranunculus has been variously stated. Some of the finest seedlings are weak, and therefore die in a few years, though for a time they had great renown; others of first rate character, are remarkably strong, and increase abundantly. A variety may be perpetuated about a century. Many of the varieties standing high in the esteem of florists forty years ago, are fast declining in numbers and energy; they now blossom less frequently, or produce smaller blossoms. Seedlings possess all the luxuriance and vigor of youth, and produce larger and finer blossoms than the old varieties. "* Similar observations might be quoted from papers in the Gardener's Chronicle, by Dr. Horner, Mr. R. Lymburn, and other cultivators of this flower.