A disease of the potato. "Any one can ensure the occurrence of this disease by keeping the sets in a situation favourable to their vegetation, as in a warm damp outhouse, and then rubbing off repeatedly the long shoots they have thrown out. Sets that have been so treated I have invariably found produce curled plants. Is not the reason very apparent ? The vital energy had been weakened by the repeated efforts to vegetate; so that when planted in the soil, their energy was unequal to the perfect development of the parts; for the curl is nothing more or less than a distorted or incomplete formation of the foliage, preceded by an imperfect production of the fibrous roots.

"The variety employed was the Early Shaw. An equal number of whole mo-derately-sized potatoes, that had been treated in three different modes, were planted the last week of March.

"No. 1. Twenty sets that had been carefully kept cold and dry throughout the winter, firm, unshrivelled, and with scarcely any symptoms of vegetation.

"No. 2. Twenty sets that had been kept warm and moist, and from which the shoots, after attaining a length of six inches, had been thrice removed.

"No. 3. Twenty sets that had been kept warm and moist for about half the time that No. 2 had, and from which the shoots, three inches in length, had been removed only twice.

"All the sets were planted the same morning, each exactly six inches below the surface, and each with an unsprout-ed eye upwards. The spring was genial.

"Of No. 1, nineteen plants came up. The twentieth seemed to have been removed by an accident. Of the nineteen not one was curled. The produce, a full average crop.

"Of No. 2 all came up, but from ten to fourteen days later than those of No. 1, and three of the plants sixteen days later. Fourteen of the plants were curled.

"Of No. 3 all came up, but from ten to fourteen days later than those of No. 1. Four plants were as severely curled as those in No. 2, eight were less so, and the remainder not at all; but of these the produce was below an average,and a full fortnight later in ripening.

"Dickson, Crichton, Knight, and others, have found that tubers taken up before they are fully ripened, produce plants not so liable to the curl as those that have remained in the ground until completely perfected; and I believe under ordinary treatment this to be the fact, for it is rational. The process of ripening proceeds-in the potato, as in the apple, after it has been gathered; and until that is perfected it is accumulating vigour, shows no appetency to vegetate, consequently is not exhausting its vitality, which is a great point, considering the careless mode usually adopted to store them through the winter; for this energy commences its decline from the moment it begins to de-velope the parts of the future plant. Tubers taken from the soil before perfectly ripe, never are so early in showing symptoms of vegetation. Crichton, Hunter, and Young, in some of the works before referred to, have also agreed, that exposing the sets to light and air, allowing them to become dry and shrivelled, also induces the curl in the plants arising from them.

This result of experience also confirms my conclusion, that the disease arises from deficient vital energy; for no process, more than this drying one of exposure to the light and air, tends to take away from a tuber the power of vegetating altogether.

"Every one acquainted with the cultivation of the potato, is aware of the great difference existing in the varieties; as to their early and rapid vegetation, those that excel in this quality are of course the most easily excitable. A consequence of this is, that they are always planted earliest in the spring, before their vital power has become very active; and of all crops, practice demonstrates that these early ones are least liable to the curl. But what is the consequence, on the contrary, if an early variety is planted for a main crop later in the spring, when extraordinary pains in keeping them cold and dry have not been employed to check their vegetation, and consequent decrease of vital energy? Such crop, then, is more than any other liable to the disease, and a good preventive has been suggested by Dr. Lindley, namely, that of planting the tubers in autumn, immediately after they have ripened. The results of my view of the disease, sustained by numerous experiments, are, that it will never occur if the following points are attended to: - First, that the sets are from tubers that exhibit scarcely any symptoms of incipient vegetation; to effect which they ought, throughout the winter, to be preserved as cool and as much excluded from the air as possible.

Secondly, that the tubers should be perfectly ripened. .Thirdly, that they should be planted immediately after they are cut. Fourthly, that the manure applied should be spread regularly, and mixed with the soil, and not along a trench in immediate contact with the sets. Fifthly, that the crop is not raised for several successive years on the same area." - Principles of Gardening.