260 POMOLOGY 



stunted growth or soon recover, depending on the extent 

 of the injury and on the growing conditions immediately 

 following planting. Mature trees in some sections are often 

 "black hearted" throughout their lives with no apparent 

 incapacity. 



229. Sun-scald is manifest by a dead area on the south- 

 west (sun-exposed) side of the trunk of the tree. This dam- 

 age, unlike the other forms discussed above, occurs late in 

 the winter when days of bright sunshine follow cold nights. 

 The cause has usually been assigned to a starting of growth 

 or sap movement on the side of the tree exposed to the sun 

 which activity is inmiediately followed by severe freezing. 

 However, Chandler does not credit this view from his work 

 with winter injury but suggests that the tissue is warmed 

 by the sun until the temperature nearly reaches the freezing 

 point when a sudden drop will cause the tissue to ''freeze 

 to death." ^ 



230. Root-killing. — -This form of injury is likely to be 

 general during a severe winter when the ground is bare. It 

 is well known that bare ground will freeze much deeper than 

 when the surface is protected by some sort of cover, but 

 no cover of vegetation is equivalent to a deep snowfall which 

 lies on the ground throughout the winter." Such hardy va- 

 rieties as Mcintosh and Wealthy will be root-killed as readily 

 as the more tender sorts, like Baldwin and Wagener, in a 

 snowless winter, although the trunks and branches of the 

 latter varieties would show severe injury while none might 

 appear on the hardy sorts. 



Chandler has shown that the roots are the tenderest part 

 of the tree, and that the portions nearest the crown are the 

 most resistant, while the smaller remote rootlets are the most 



' See also Mix, A. J. Sun-scald of fruit-trees a type of winter injury. 

 Cornell Univ. Agr. Exp. Sta. Bull. 382. 1910. 

 2 Neb. Agr. Exp. Sta. Bull. 79, 92. 1903, 1906. 



