POTATO DEVELOPMENT WORK IN WISCONSIN. 39 



on the screen will produce a large number of shapely good sized 

 tubers, while others like the one you now see produce a large num- 

 ber of small irregular tubers, and are absolutely worthless. Some 

 tubers are white skinned, some flesh, some red, and some arc a 

 bluish black, with all intergrading shades of these colors. The 

 seedlings of some parents produce nothing but white tubers ; in 

 other parents they will run from white to a deep red; while in 

 still others the blues and bluish black appear. The latter color 

 appears only Avhen certain parents are used. 



Few of us can afford to grow seedlings because it involves a 

 good deal of work, and the chances of producing a really desir- 

 able variety are so few that it is hardly worth the effort. On 

 the other hand none of us are too busy or should not be, that 

 we cannot practise seed selection on the varieties we are grow- 

 ing. 



SELECTION AND WHAT IT IMPLIES. 



Our present day interpretation of plant breeding includes both 

 the selectionist and the hybridist. While there is no particular 

 objection to this interpretaioii it has always seemed to me that 

 the improvement of asexually propagated plants by selection 

 alone docs not necessarly constitute plant breeding. It would be 

 preferable to restrict the term to the process of improvement by 

 means of sexual reproduction. Intelligent plant breeding under 

 this definition involves the selection and crossing of parent plants 

 possessing certain desirable attributes which it is proposed to 

 unite in a single individual. The resultant progeny from such a 

 cross must be carefully studied and rigidly selected for the parti- 

 cular attributes desired. According to this definition it is seen 

 that successful plant breeding is not independent of selection. 



The selectionist on the other hand can carry on his work inde- 

 pendent of sexual reproduction. The improvement which may 

 result from selection alone is limited to natural variations which 

 may occur within the variety that he is endeavoring to improve. 

 Inasmuch however as considerable variation may be found in 

 most of our cultivated varieties the limitations are by no means 

 so restricted as one might expect. Our former concept that a 

 variety was a fixed entity has now given away to in acknowledg- 

 ment that it may possess one or more entities. 



The selectionist recognizing this fact proceeds to isolate cer- 

 tain races or types which seem to him to be an improvement over 



