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I believe, most satisfactory evidence, tliat tlie plant, considered as a spe- 

 cies, has progressively deteriorated. For a long time it appears to have 

 continued free from any observable disease ; and the first mild form of 

 disease "curl," and the more recent and fatal "dry rot," I found could 

 not be attributed solely to any peculiarity of soil, season, or mode of cul- 

 ture, but were peculiar to, and therefore inherent in, certain varieties for 

 the time being. And not only are there abundant proofs that the pota- 

 toe generally is in a degenerate condition, but there is evidence that ^ ari- 

 eties have been mostly injured by the mildew in proportion to the symp- 

 toms of debility which they had previously exhibited, whilst some recently 

 obtained from seeds, more especially in Germany and Prussia, are said, 

 to have remained entirely unharmed, though growing in the vicinity of 

 others which were affected. If the facts be so, can any thing be more 

 obvious than that a most certain means of preventing or mitigating the 

 effects of the blight, is by increasing the constitutional vigor and hardi- 

 ness of our potatoe crops. How then is this to be accomplished? " We 

 could answer this question with most confidence if we knew the precise 

 causes which have led to the deterioration of the potatoe. Over-manu- 

 ring, cutting the tubers into sets, planting the sets on raw manure, imper- 

 fect storing of the seed-tubers during winter, have each been supposed to 

 be the cause of degeneracy. These, with many other causes, may have 

 contributed to the bad health of varieties, and may thus have hastened 

 the deterioration of the plant as a species. The present condition of the 

 potatoe is probably the accumulative result of not one, but several ad- 

 verse influences operating through successive generations. 



The degeneracy of the potatoe plant is, I believe, owing chiefly to the 

 mode in which it is usually propagated. Plants propagated by extension, 

 that is, by buds, cuttings, laj^ers or roots, are but the extension of an in- 

 dividual, possessing the same constitution, properties and tendencies, and 

 are not a renewal or reproduction as by seed. A variety so propagated 

 bas a determinate existence, there comes a time sooner or later, accord- 

 ing to the original vigor of the parent plant, and to the treatment its 

 progeny receives, when it will become comparatively worthless, and cease 

 to deserve the attention of the planter. Andrew Knight, who first estab- 

 lished this fact, by numerous experiments on various plants, continued 

 through many successive years, said, in the last letter he wrote on the 

 potatoe, "that varieties, which have been long cultivated, cease to be 

 equally productive, is placed beyond the reach of controversy. I baye. 



