EXPERIMENT STATION BULLETINS. 



345 



stems in the hill. A productive single stem hill should produce four or more 

 good tubers. A hill with two or more stems may produce six or more pota- 

 toes and yet not have as good yielding quahties as the one-stem hill that 

 grows four tubers. After the best hills have been saved for the next year's 

 seed plot, the poorest hills, that give low yields of poor quality potatoes, 

 should be picked up and kept separate for eating purposes. Then the re- 

 maining hills are harvested and saved to plant the main crop the next year. 

 It has been proved that if this method of selection is followed consistently, 

 it will in a few years time give increased yields of twenty per cent or more, and 

 that the quality of the potatoes will be improved. 



Fig. 9. A crate of choice seed potatoes of the Late Petoskey (Russet Rural) variety. 



Seed potatoes should not be saved from those plants that have an excep- 

 tionally vigorous, upright habit of growth. This type of plant termed 

 "giant hill" remains green very late in the season. It is quite immune to 

 leaf-hopper and foilage disease injuries and is generally resistant to light 

 frost. Potatoes from such plants produce poor yields of inferior quality. 



Growers whose seed potatoes contain varietal mixture and diseases, and 

 which are not giving satisfactory yields would do well to buy at least a few 

 bushels of Michigan Certified Seed Potatoes and grow them in comparison 

 with their own stock. The tests that were made with Michigan Certified 

 Seed in 1921, in Michigan and in other states, showed that the certified seed 



