30 BOARD OF AGRICULTURE. [Pub. Doc. 



and he has told me of its natural habits. This plant has 

 been in common culture by white men for less than two cen- 

 turies ; and, indeed, it is within a generation that Goodrich 

 and .others have brought new strains from their tropical 

 homes and developed from them the best of our present 

 varieties. Now, what is the result? Our northern season 

 of growth is shorter by one-third or even one-half than that 

 of its natural habitat. There, the potato plant reproduces 

 itself primaril}^ by seeds and secondarily by tubers. Here, 

 by intensive breeding, selection and high culture, man has 

 so changed the conditions that seed production is almost un- 

 known, while the size of the tubers is enormously increased. 

 In Mexico and southward it starts into growth in March, 

 and reaches full maturity in December, — a season covering 

 tln-ee-quarters of the year, as contrasted with ours of from 

 three to five months. There the period of blossoming and 

 seed maturing occurs in August and September, whereas the 

 tuber formation follows after the ripening of the seed, dur- 

 ing the last two months of the growth. Now, reproduction 

 by seed is a sexual process ; that by tubers is vegetative. 

 Both are exhaustive of the vital forces of the plant. In a 

 certain phvsiological sense the two are opposed to each 

 other, representing opposite tendencies within the plant, 

 therefore, they cannot well he carried on by the plant at the 

 same time. In the natural state of the potato they are not. 

 As we have explained above, seed formation precedes by 

 some weeks, the long season of growth there permitting this. 

 But with the cultivated potato in our short season and under 

 intensive culture we have crowded the two processes together 

 till thev overlap. Dig up a potato plant when in blossom, 

 and you will find it starting to form tubers also. That is, we 

 have forced tuber production back into the period which in 

 the wild plant is given to the formation of flowers and seeds. 

 According to the mode of life of its ancestors, such a plant 

 should be throwing all of its energies upward to perfect the 

 flower and mature its seed balls. But tuber production in our 

 highly specialized garden plant immediately laj^s claim to the 

 major part of the reproductive energies of the plant. As a 

 result of this conflict of tendencies in the plant, there occurs 



