268 



Journal of Agricultural Research voi. xvii, no. 6 



Table VIII. — Hill selection: Effect of mosaic of potato on vines in laboratory plots, 

 Presque Isle, Me., IQ18 



From these data it is apparent that progeny from plants seeming to 

 be healthy in one season may develop both healthy and diseased stock 

 the following season. It will be noted further that the mottling on this 

 control stock the following season may develop to such a degree that it 

 falls under all three stages, slight, medium and bad, and does not neces- 

 sarily begin with a slight stage as one might expect. Furthermore, it is 

 shown that mottled and nonmottled plants may develop from the same 

 hill and even from a single tuber, similar observations having been 

 recorded by F. C. Stewart (/o). 



The observations regarding degree of mottling and dwarfing in the 

 control stock also obtained in the slight, medium and bad stages. In 

 none of these stages did the stock necessarily run true to the stage for 

 which it was selected. It will be noted also that mottled foliage devel- 

 oped wherever the progeny came from plants showing the slight, medium, 

 or bad stage the previous season. In but two strains where the foliage 



