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twice daily. The bulb of the thermometer was placed on a level 

 with the terminal bud of the tubers. The variation among the 

 different pots was always less than a degree. The average tem- 

 perature one inch below the surface of the soil in pot i, table XIV, 

 was i8?5 C. for the 135 days. 



The elimination of the rest period by removing the skin is not 

 due to water absorption from the exterior, as tubers with the skins 

 removed will sprout even in dry storage much earlier than those 

 with skins intact; see table XVII. 



TABLE XVII 



Effect of cutting the tubers in half. — All the experiments 

 so far reported were conducted with whole tubers, in which case 

 sprouting always began first from the eyes on the seed end. The 

 reverse is true, however, when the tubers are cut in half transversely 

 to the long axis, separating the seed from the stem end. This 

 applies only to tubers forced to sprout during the natural rest period. 

 At the end of the rest period there seems to be little difference, in 

 respect to time of sprouting, between the eyes on the seed and stem 

 ends if the tubers are cut in half. 



On October 31 the skin was removed from tubers harvested on 

 October 28. They were then cut in half. The halves were stood 

 upright on wet soil and covered with wet excelsior. On Novem- 

 ber 15 all the stem halves bore sprouts from eyes located near the 

 cut surface. 



Two lots of 4 tubers each were selected from McCormick pota- 

 toes harvested on November 4. On November 8 the tubers were 

 cut in 4 pieces in the manner shown in fig. 1 . In addition the skins 



