Killing of Plant Tissue by Low Temperature 



221 



In case of apples and peaches the young leaves are miiformly 

 more easily killed, while in the case of some of the succulent plants 

 there is little or no difference. In case of lettuce the young leaves 

 are certainly the more resistant. The density of the sap of tiie oKl 

 peach leaves was such that an average of ten freezing point iletor- 

 minations gave a depression of 1.031 while for the young leaves the 

 depression was 1.663. With the Jonathan apple, the depression for old 

 leaves was 1.849 while for young leaves it was 1.202. With these leaves 

 then it seems that the greater sap densil>- will exj-lain the greater 



