410 BULLETIN No. 127. [August, 



6. HYPOTHESIS OF DEGENERATION 

 ANALYSIS OF THK QUESTION 



Very closely linked with the possible improvement of varieties 

 by the selection of favorable fluctuations, and its equal in economic 

 importance, is the alleged phenomenon of degeneration. The com- 

 mon idea is, that there is a weakening, "a running out" of a variety, 

 so that varieties within a greater or less number of years are cer- 

 tain to become worthless for cultivation. That certain varieties in 

 certain localities do lessen in vigor from year to year is not to be 

 disputed. The question is are there contributing causes, or is it an 

 inner physiological weakening, a protoplasmic degeneration, which 

 must take place owing to long continued bud propagation. The 

 proper analysis of the question is of great importance; for, if such 

 a degeneration must take place through obedience to physiological 

 laws, our good varieties are necessarily doomed to a limited life. 

 A proof that this is true, would make a great difference in the 

 practicability of methods of tuber selection, where the improvement 

 if granted possible would at least be. slow. Methods of selec- 

 tion to change the composition, involving expensive analyses of 

 mother tubers, as in the case of sugar beets, would be absolutely 

 prohibited unless the sexual transmission of these acquired char- 

 acteristics could be shown. 



The common method of reasoning has been: Varieties have 

 diminished in yield in certain places, and other varieties have been 

 obtained. Nothing more is heard concerning the first varieties; 

 hence, it is concluded that they have declined, and, figuratively 

 speaking, died. 



Hays ( 52) x indicates the general belief in the following state- 

 ment : 



"The age to which a variety propagated by annually planting the root cut- 

 tings of a single seminally produced plant will live before the necessity of 

 renewal by sexual reproduction is not known. But since standard varieties of 

 potatoes remain prominent for only about a third of a century there is some 

 reason for the belief that the varieties reach their period of old age or senility 

 in that time." 



The period of prominence of varieties is hardly a measure of the 

 question, for hundreds of men are annually growing seedlings with 

 which they hope to supplant current varieties and it would be re- 

 markable if many old varieties were of sufficient merit successfully 

 to hold their own. But nevertheless, even if the latter statement 

 were not true, only a portion of the question is settled, Ehrenberg 



