6 



several stocks have found their way to Europe, and it 

 is doubtless due to the different stocks that so much 

 variation in shape, colour, habit of growth, and other 

 characteristics is met with among the varieties in 

 cultivation to-day. 



Effect of Cultivation on the Plant. 



Had but one stock been available it is probable that 



k 



the plant would have suffered more from in-breeding 

 than it has, although there is little doubt that too close 

 breeding is the cause of much of the physical weakness 

 apparent in modern varieties. Throughout the cen- 

 turies the potato has been in Europe it has been sub- 

 jected to systems of cultivation which have tended to 

 develop the tuber at the expense of the seed, Com- 

 paratively few of the solanaceous plants produce tubers; 

 the life of almost all is perpetuated from year to year 

 by seeds. There appears to be considerable doubt as 

 to why the varieties which bear tubers should have 

 developed this peculiar method of reproducing life 

 from year to year ; but it appears to be a special pro- 

 vision of nature to meet the exigencies of the exceed- 

 ingly hot and dry climates in which they are found 

 growing wild. Under ordinary conditions the seed of 

 a plant is produced in a climate which is favourable for 

 its germination and growth ; consequently, there is no 

 need to provide special means for its propagation. In 

 climates like that of Chili the growth of potatoes from 

 seed, through want of moisture sufficiently early in the 

 season, might be impossible. Nature appears to have 



