104 AGRICULTURE 



selecting seed from the potato bin, any more than the best 

 seed corn can be selected from the crib or wagon. For a 

 certain tuber may itself be of good size and look promis- 

 ing, but have come' from a plant that produced but one or 

 two potatoes, or that grew only one tuber of fair size, 

 with several culls. 



The most successful method of developing high-grade 

 seed potatoes is what is called the tuber-unit method. This 

 consists of selecting from the seed bin a quantity of the 

 most perfect tubers, each to weigh from six to eight ounces. 

 These are cut for planting by splitting the tuber into four 

 quarters, from seed end to stem ^nd. 



The tuber-unit method. The four pieces of each po- 

 tato are planted in succession twelve inches apart in the row. 

 A longer space is left between the sets of fours, thus mak- 

 ing it possible to watch the outcome of each tuber by itself. 

 Before the plants begin to die, careful inspection is made, 

 and any mixtures, imperfect or weak plants are marked for 

 rejection. Only the most promising and uniform are re- 

 served for the selection of seed. 



When the crop is harvested, each set of four is dug by 

 itself. A further selection is made by rejecting the total 

 product if any one of the four plants has failed to pro- 

 duce uniform, desirable tubers. The potatoes produced by 

 each set of four selected for seed are put into separate sacks 

 and kept for further examination. 



Second season of tuber-unit planting. Finally, the 

 contents of each sack ?.re inspected for the weight of mar- 

 ketable and unmarketable tubers, and other desirable qual- 

 ities of the type. From each of the four-plant units the 

 best ten tubers are to be selected for the next year's plant- 

 ing. This selected seed is planted the following year in 

 the same way as the first season, thus giving forty plants 

 to the unit instead of four. The product from the best forty- 



