662 POTATO ROT. 



the death and consaqnent putrefaction of parts of the tissues of 

 the plant. Further, the analogy of other vegetables leads us 

 to believe that plants do not always simply die out, under the 

 influences of degeneracy or old age. The worn out carnation 

 loses the size and brilliancy of its flowers; the old varieties of 

 fruit trees lose their vigor of growth, degenerate in their fruit, 

 and become very liable to the attacks of parasitic fungi and an- 

 imals ; the ancient forest, its trees decaying at the heart, and 

 overgrown externally with lichens, mosses, fungi, and excres- 

 cences, usually perishes by tempests or fires, before it undergoes 

 the slow process of natural death. So with the potato. Under 

 high cultivation, its starchy and albuminous parts, those which 

 are valuable for human food, have been increased, while, by 

 constant reproduction from the roots, the vitality of the living 

 buds has been diminishing. The potato, at one time the most 

 certain and hardy of crops, has gradiially become tender. The 

 " curl" and " dry rot" began twenty years ago to cut ofT the 

 young shoots and the planted tubers, apparently because there 

 was not sufficient vegetative life to enable the living bud to 

 control and use the abundant nutriment for it in the cells of 

 the tuber. This difficulty was overcome in part, by changes 

 of seed, planting whole tubers, and other expedients ; and the 

 life of the plant v/as protracted a little longer, as might have 

 been expected, to be attacked only by some worse disease. 

 And now we have to contend with a mortification of the 

 tissues, not in the infant stage, but in the period of the plant's 

 fullest vigor and strength. 



It may be objected, however, that even renewal from the 

 ball has not been effectual, the seedling varieties having suf- 

 fered as well as others. It must be observed, however, that 

 seedling varieties have generally resisted the disease longer 

 than others, and that there seems good reason to believe that 

 the disease, like most others that originate, whether in plants 

 or animals, from long exposure to debilitating influences, is 

 more or less contagious. It is quite probable also, that the seed 

 of plants which have already contracted the disease, may be 

 itself not quite free from hereditary taint. Renewal from the 

 seed cannot, therefore, be assumed to have been fairly tried. 



