POTATO ROT. 661 



plant occupy its place, it must be a seedling produced from the 

 balls which have fallen on the spot. 



If then, since the potato was introduced into Europe about 

 250 years ago, we have been continuing its cultivation solely 

 by division or separation of the tubers, we have been perpetu- 

 ating the life of one individual plant ; and we must have now 

 potatoes that are the descendants of those imported by Raleigh, 

 not by natural generation through the seed, but by indefinite 

 division of the plant, a sort of infinitesimal fractions by a per- 

 petual division of that now extremely aged individual potato. 

 Have we a right to expect that such plants should be healthy? 

 We may not know the minute changes which bring about 

 the debility of age, but we know that such debility does over- 

 take plants, as well as animals. Fine varieties of carnation 

 propagated by cuttings or layers, in a few years degenerate, and 

 must be abandoned by the florist. The same happens to other 

 florists' flowers, though in some more slowly. Grafting and 

 budding fruit trees, is but continuing the lives of individuals, 

 and despite the vigor of the new stock, grafts from very aged 

 trees of old varieties, show the debility of the parent. Hence, 

 most of the finest fruits of a century or two ago, have degener- 

 ated and become less worthy of cultivation, and have been re- 

 placed by new varieties from the seed. This seems to be one 

 of the great laws of vegetable life, and accordingly even those 

 plants which, like the potato, have been furnished with tubers 

 to provide for the continuance ofindividual life, have also been 

 provided with seeds to produce new individuals, and thus per- 

 manently continue the species. 



Taking this view of the matter, we should rather wonder 

 that the potato has lasted so long, than that it now fails. We 

 can, in truth, account for its long duration, only by taking into 

 consideration the varieties of soils and climates in which it has 

 been cultivated, the frequent changes of seed, and the occa- 

 sional raising of new varieties from the ball. 



If, however, this cause has had any real influence on the 

 plant, why has it not merely run out or died of old age, instead 

 of contracting a malignant and fatal disease. In answer to this, 

 I may remark that the disease in question is, in fact, merely 



