190$.] IMPROVEMENT OF THE POTATO. 411 



(29) has lately discussed the question in all of its bearings from 

 the practical standpoint, and divides it into three parts : ( i ) the 

 aging (Altern) or senility of a variety, that is, a degeneration re- 

 sulting from inner causes because of a prolonged and possibly un- 

 natural propagation by means of tubers; (2) the deterioration 

 (Ausarten) caused by a change to an unfavorable environment; 

 (3) the loss of vigor due to lack of selection of the tubers (Herab- 

 ziichtung). It seems that the last two might be united, for, set- 

 ting aside the first question, it must be variation in outside influ- 

 ences .that causes sufficient variation in individual plants to make a 

 basis for selection. We would then have the questions of variety 

 senility, and of incomplete adaptation. 



The latter question is one of such common knowledge that it is 

 hardly necessary to discuss its voluminous literature. It should be 

 noted, however, that this has nothing to do with the question of the 

 inheritance of partial fluctuations. 



In a letter written by Joseph Cooper (5), of New Jersey, in 

 1799, and published in volume one of the Memoirs of the Philadel- 

 phia Society for promoting Agriculture, the matter seems to be gen- 

 erally recognized. For fifty years, Cooper had maintained and 

 improved without change, strains of pumpkins, early peas and as- 

 paragus. "He made similarly successful experiments in keeping 

 and improving strains of the potato for even at that time the com- 

 plaint was 'very general,' as he writes, 'that potatoes of every kind 

 degenerate.' ' 



The idea has changed little among farmers today, although 

 some light has been thrown on the question. In 1876, Beal (8) 

 reported an experiment in which a variety giving good yields de- 

 generated in eight years so as to produce nothing, although other 

 varieties were producing good crops on the same soil. Fruwirth 

 (42) and Martinet (70) have explained this and the other numer- 

 ous experiments of the same nature by showing that there is a 

 gradual change of characters that takes place upon changing the 

 locality, either for better or worse conditions. In other words, a 

 variety coming from a locality favorable as to soil and climate 

 to one unfavorable, is not able to adapt itself rapidly to con- 

 ditions, as are seed propagated plants by means of their possibil- 

 ities for greater numbers of combinations of characters. There- 

 fore there is a final disclosing of the inadaptibility of the variety, 

 although it takes place more or less slowly owing to the same law. 



It seems to the writer that the main economic question still un- 

 solved is whether there is a gradual reduction of disease resisting 



