60 The Sweet Potato 



of different varieties should never be mixed. In gen- 

 eral, it may be said that painstaking hill selection 

 should be practiced in the fall at digging time, the po- 

 tatoes selected being carefully saved in a storage-house 

 and culled over in the spring. Medium-sized or small 

 tubers are preferred. 



Production of seed potatoes. 



Some growers have adopted a systematic method of 

 producing their seed stock with a view to the elimina- 

 tion of disease, improvement in quality and economy 

 and convenience of growth without going through the 

 entire field each year. One system is managed on the 

 same principle as the " ear-to-row " test in seed-corn 

 selection. A special seed patch is prepared. Medium- 

 sized well-shaped potatoes are selected from high pro- 

 ducing hills and enough are bedded to produce slips 

 for the seed patch. The following year the same care- 

 ful hill selection is made from the seed patch for tubers 

 to bed for select plants the next year, the remainder of 

 the seed-patch potatoes, whether from high yielding 

 hills or not, being used to bed for the main field crop. 

 This practice is probably justifiable when planting is 

 done on a large scale and when wholesale selection of 

 tubers for the entire field crop would have to be trusted 

 in the hands of unreliable farm labor. The specialized 

 production of seed stock from vines has been found of 

 value, especially in the control of disease and in the 

 better keeping quality of potatoes produced in this 

 way. 



Seed treatment. 



Even though careful culling of bruised and diseased 



