Potato Breeding 65 



four liills and then go over the row and cut each tuber and plant 

 its quota of four hills. The hills in the row should be planted some- 

 what farther apart than in ordinary planting, probably 20 to 24 

 inches. If this is not done, a somewhat greater distance than ordinary 

 should be left between each two four-hill tuber-units. The writer 

 would advise that one hill be left unplanted between each two four- 

 hill units. It would doubtless be convenient and desirable to have 

 the plants in rows both ways to facilitate digging. For this selec- 

 tion-plot of potatoes, choose a field of moderately good fertility and 

 as uniform throughout in soil as it is possible to obtain. 



(4) Manm"e and cultivate the plot of potatoes grown for selec- 

 tion just the same as you do your ordinary crop. 



How to make the selection of potatoes — field examination. — A 

 careful examination of the selection field should be made as the 

 vines begin to matiu-e and while they are yet green. This examina- 

 tion should include observations on diseases and vigor of the tops. 

 If there are any marked differences apparent between the different 

 four-hill units, those with the best-appearing, most healthy tops 

 should be marked by small stakes which can be stuck in the ground 

 beside the hills. This field examination, while important in careful 

 work, probably could be omitted without very great loss, as after all 

 the yield is tlie primary character. 



Digging the selection field. — The digging of the field grown for 

 selection purposes requires considerable care, and here hard work is 

 necessary. Dig each four-hill unit grown from the same tuber sei)a- 

 rately, being careful to get all of the product, and avoid cutting or 

 injm-ing the tubers if possible. Carefully place the product of each 

 foiu"-hill tuber-unit together at one side of the row, and if it is a tuber- 

 unit marked with a stake in the field examination, keep the stake 

 with the product of the unit. A good way to dig in order to avoid 

 getting the hills of different tuber-units mixed is to dig across the 

 field, in a direction at right angles to the direction the rows were 

 planted. First dig the four hills of the first tuber planted in the first 

 row, then the four from the first tuber in the second row, then the 

 same in the third row, fourth row, etc., tlirough the field. Next 

 dig the foiu" hills from the second tuber planted in the first row, then 

 the four from the second tuber in the second row, etc. By this 

 method of digging, especially if the hills are rowed both wa^'s, there 

 will be little danger of mixing the product of the four-hill units. 



Making the selections. — The problem after digging is to select 



