A Study of Quality in Potatoes. 225 



when fresh dug, and tends to become netted when mature. The 

 tops grow large and vigorously and are fairly resistant to disease. 

 During the growing season of 1903, no data upon soil or air tempera- 

 ture were recorded, but it was ascertained upon careful examination 

 and study, that tubers of this variety growing at different depths 

 varied in cooking quality and it was further observed that structural 

 characteristics varied with the depth at which the tubers grow. It 

 was supposed that the temperature and possibly the moisture con- 

 tent of the soil, had throughout the growing season an influence 

 upon these characteristics of the tubers. In order further to investi- 



FiG. 179. — Cross-section from the stem end of a tuber three inches long, growing %n 

 a sloping position with bud end one inch below the surface. The section was one 

 centimeter thick and boiled for twenty minutes. Compare Figs. 180 and 181 from 

 the same tuber. 



gate these influences during the season of 1904 the same variety of 

 potatoes was planted May 12, on three adjacent plats, at depths of 

 two, four and six inches. The temperature was taken by the electric 

 method devised by the Bureau of Soils, Washington, D. C, and 

 described by El wood Mead and Lyman J. Briggs in Bulletin 15 of the 

 Bureau of Soils. Resistance coils were planted in duplicate, in the 

 middle row of each plat at such points as would promise uniform 

 temperature readings. These were planted in a horizontal position 

 at the same depth as the potatoes in their respective plats. During 

 the growing season, from May 14 to Sept. 24, the temperatures 

 15 



