222 AGRICL'LTURE OF MAIXE. 



AFTERXOOX SESSION. 



In the absence of the President the afternoon session was 

 called to order by A. P. Howes, Mce-President. A most inter- 

 estin paper was presented by Dr. Raymond Pearl on 



SO^IE FACTORS IX POTATO IMPROVEMENT. 



The following points were discussed : — 



1. In every plant and animal there are limitations set to the 

 possible improvement of that plant or animal by (3.) the 

 method or mechanism of inheritance peculiar to it, (b) the 

 frequency and regularity of occurrence of desirable and inherit- 

 able variations, and (c) the method of reproduction. 



2. In the potato the most important of these limitations is 

 found in the method of reproduction. The potato is propagated 

 vegetatively : that is, by setting out annually what amounts to 

 cuttings from the plant grown the year before. A potato tuber 

 is not a seed in the botanical sense : it is a part of the stem of 

 the potato plant, and the eye is a bud. 



3. This being so, tuber selection, however long continued, 

 is not likely to originate new and desirable varieties. The only 

 possibility of this happening would be through the occurrence 

 of inheritable bud variations of a desirable sort. Such inherit- 

 able bud variations apparently do not occur with great fre- 

 quency in the potato. 



4. Tuber selection, however, may be a very desirable thing 

 to practice, for the purpose of purifying the stock which one 

 is using for seed. Most varieties of potatoes undoubtedly 

 represent mixtures of varying numbers of true strains of bio- 

 types. Tuber selection may be very valuble in isolating and 

 preserving desirable strains or biotypes from the mixture, and 

 discarding undesirable biotypes. 



5. One should not expect continued improvement to follow 

 tuber selection. In the nature of the case this is not to be 

 expected, and if one fails to get it he should not indiscriminately 

 condemn the whole practice of tuber selection. 



6. The histories of the existing commercial varieties of 

 potatoes, so far as these histories are known, indicate that 



