I 9 o8.] 



IMPROVEMENT OF THE POTATO. 



409 



The exception in the case of Magnum bonum is explained by 

 the fact that the seed of the crop from this variety was mixed in 

 1899 and the small potatoes used here may have been from large 

 yielding vines before that. He concludes : "It is now without 

 question to me, that we are able to raise the yield of potatoes by a 

 not inconsiderable degree through the slight care in selection of 

 seed, and also to prevent to a very great degree the degeneration 

 of the newly improved variety." 



Later Martinet (71), Krzymowski (62), Eustace (31) and 

 Parisot (78) have experimented along this line, but they have not 

 generally carried on their investigations long enough to warrant 

 definite conclusions. 



Summing up all evidence, it appears that there are variations 

 which may be transmitted in tuber propagation, but that in prac- 

 tice a gain is rarely made by their selection. In general, results 

 have been obscured by seasonal, climatic and local soil conditions 

 which have a tremendous effect and which are not constant enough 

 to permit tracing marked hereditary transmission. The changes 

 that have been made in certain cases may be entirely due to muta- 

 tions and not fluctuations; or they may be due to the comparison 

 of tubers that were physiologically different, such as diseased and 

 healthy, or immature and mature tubers. Proper conclusions can be 

 drawn only after controlled experiments upon an accurately meas- 

 ured character by the use of biometrical methods. 



