230 The Rev. E. Cartwright's Eisay on 



This reasoning is confirmed by the practice of the potatoe-farmers in Yorkshire. 

 In Marshland, a district in that country, which supplies the London market with 

 the greatest part of its potatoes, it is customary to plant potatoes in the same field 

 for twenty years in succession, manuring for them every other year. No com- 

 plaints are made, that the crops are less productive now, than they were formerly, 

 or that the potatoes degenerate. 



It may not be improper, however, to remark, that it is more than probable that 

 every agricultural plant would not admit of being cultivated in the same field for 

 a series of years, like potatoes. Such plants, for instance, as are liable to be infested 

 by particular insects, ought not to be repeated too often in the same field ; as the 

 insects, it is reasonable to conclude, would multiply in a soil which regularly sup- 

 plied them with food ; for it is a natural supposition that where the insect finds its 

 food there it will deposit its eggs, or remain buried in the ground in its larva state 

 till the returning season. 



Upon this principle, perhaps, we may account for the circumstance respecting 

 red clover, taken notice of in many parts of Suffolk and Norfolk, namely, that the 

 land, as the farmers there express themselves, is grown tired of it. It is not impro- 

 bable that some insect, too minute for general observation, and which for a number 

 of years has been increasing in the soil, may prey upon the young fibres of the root, 

 or some other delicate part, so as either totally to destroy the plants, or to render 

 them weak and sickly. Should this reasoning be conclusive when applied to red 

 clover, which is never repeated oftener than once in every four years, it must appear 

 still more conclusive when applied to insect-feeding plants repeated on the same soil 

 every year. 



It is generally supposed that the colour of the potatoe blossom depends upon the 

 colour of the potatoe ; that a white blossom, in short, is a certain indication that 

 the potatoe to be produced will be white, and that the purple blossom as infallibly 

 shews that it will be red. This, however, is a mistaken supposition ; the white blos- 

 som invariably indicating that the po;atoe which produces it is of the kidney kind; 

 the blossoms of the red being only of a darker hue. There is, I believe, no instance 

 of a true kidney-shaped potatoe being red. 



Having in a preceding part of this paper spoken of the potatoe as a plant remark- 

 ably tenacious of life, it may not be improper to mention that it possesses also a 

 principle of vitality, or self-propagation, which few persons, it is believed, suspect. 



