126 AGRICULTURE 



evenly. Thus, when the earlier variety has ripened and 

 is ready for the market or table, the later one will have 

 the potatoes just setting, and unfit for use. Mixed vari- 

 eties do not cook evenly, and when baked or -broiled to- 

 gether some will be overdone before others have softened. 

 General mixture of varieties in potatoes as in other crops 

 tends to degeneration and running out of the strain or 

 breed. 



Seed from productive plants. Seed should be taken 

 only from the strongest and most productive plants, no 

 matter what the variety. This can not be accomplished by 

 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. 



One of the most successful methods 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 end. 



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, and 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 



