"58 



Trunk-splitting, sun scald, a killing of the bark on the south 

 or southwest side of the tree which he reports very serious in north- 

 ern and eastern Ontario and in the Province of Quebec. 



Killing-back which he says results from inherent tenderness 

 of the variety, or from insufficient maturity of the wood. 



Crotch-injury, a killing of the cortex and perhaps other tissue 

 in crotches of the limbs. Macoun, Morse, and Grossenbacher have 

 studied this form of injury, and have found it to follow severe winters. 

 Macoun and Morse attribute this injury to the lodging of ice in the 

 crotch, while Grossenbacher attributes it to tearing caused by ten- 

 sions developed by the shrinking of the tissue during its frozen con- 

 dition. Grossenbacher observed this form of injury most commonly 

 in the crotch formed by vigorously growing secondary branches. 



Black-heart, a condition which follows the killing of the sap 

 wood when the cambium is left alive to form new wood outside the 

 killed area. It is troublesome to nurserymen in northern sections. 



Trunk-injury or body injury, a killing of the older parts of the 

 tree above the snow line. Macoun thinks this injury may be due 

 to loss of water while the tree is frozen. Grossenbacher 1 describes 

 a similar injury as Crown Rot, and attributes it to tearing from ten- 

 sion in the tree when frozen, and to a loss of water while frozen. 

 He seemed to find it worse on the side of the tree trunk next to the 

 prevailing winds. 



The experience of the Missouri Experiment Station where the 

 wood of the body of the tree, especially at the base of the tree trunk 

 and at the crotches, becomes hardy more slowly in autumn in some 

 years at least than does the tissue of the secondary branches or even 

 the twigs (see Table 24) may have some bearing in connection with 

 some of the above forms of injury, especially crotch injury and body 

 injury, or crown rot. It seems possible that those forms of injury 

 are merely direct freezing to death and that such injuries are more 

 commonly found at the base of the trunk, or at the crotch, because 

 on such years these are the most tender points. 



Grossenbacher thawed the bark of a tree with warm water and 

 worked the tree backward and forward when the temperature was 

 -26° C. on January 8. In March practically all of the bark was found 

 to be dead, showing apparently the characteristic browning of direct 

 freezing to death. It would seem doubtful if this condition of com- 

 plete death of the tissue with the browning would be found so soon 



•New York (Geneva) Agr. Exp. Sta. Tech. Bui. 23, 1912. (Bibl. No. 50). New York 

 (Geneva) Agr. Exp. Sta. Tech. Bvd. 12, 1909. (Bibl. No. 51). 



