DEVELOPME^'T Or TUBEKS IX THE POTATO. 7 



investigation. In 1916 the percentage of marketable tubers ^vith 

 respect to both number and weight increased up to the end of the 

 season, while in 1917 the number percentage remained nearly con- 

 stant after October 11 and the weight percentage after September 27. 



Fig. 4.— Young plant of the Irish Cobbler variety of potato, showing its root system and the starting 

 of stolons. The plants shown in figures 4 1 o6 were grown bv and photographed under the direction of 

 AV. V. Shear. 



The rate of growth was found to be very rapid during the early 

 part of the period of tuber tlevelopment. The hirgest increases per 

 week (208. 9 and 213.4 grams in 1916 and 1917, respectively) were 

 at the rate of approximately 30 grams (1 ounce) per hill for each day. 



