174 
the northeastern states. There has probably been no period 
ithin the memo: x for that matter within the 
play in regard to sus- 
ceptibility to various t 
Som 
e eoaditiéne which underlie winter-killing are as 
evere and prolonged cold, causing frost to penetrate to a 
great dep th. 
Sudden and severe cold following a prolonged warm spell in 
the fall, in which case the wood tissue may be tender and im 
atu. 
All ee which favor a soft 
iou 
th and immaturity of 
Ss causes may be 
aie for this, such as 
oist soil, too heavy manuring or fertilization, 
nlight. 
sed by insect pests and fungous 
of moisture in the soil. 
nsufficient oie covering, such as lack of organic matter, light 
mulching and thin snow covering in winter. 
