Plate XV. 



Fig. 1.— Strong and Weak Tuber Units of the Gold Coin Variety of Potatoes. 



Nos. 1 and 2 represent strong and weak tuber units in 1911; Nos. 3 and 4 represent yields from 

 tuber units 1 and 2; Nos. 5 and 6 represent yields in 1912 from five tuber units of Nos. 3 and 4. 



Fig. 2.— Strong and Weak Tuber Units of the Rural Blush Variety of 



Potatoes. 



No. 1 represents a strong tuber unit in 1911, with its 1911 yield and the 1912 yield from five 

 of its tuber units. No. 2 represents a M'eak tuber unit in 1911, with its 1911 yield and the 

 1912 yield from five of its tuber units. 



