83 



Material 



Date 



Tem- 

 pera- 

 ture 



Num 



ber 



Leaves 



De- 

 pres- 



Black Seeded Simpson 



lettuce young leaves. . . 

 Black Seeded Simpson 



lettuce old leaves 



Black Seeded Simpson 

 ' lettuce young leaves . . . 

 Black Seeded Simpson 



lettuce old leaves 



Tomato leaves, old and 



turgid 



Tomato leaves, young and 



turgid 



Flat Dutch Cabbage, 



young leaves 



Flat Dutch Cabbage, 



old leaves 



Flat ' Dutch Cabbage, 



young leaves 



Flat Dutch Cabbage, 



old leaves 



Red Rock Cabbage 



young leaves 



Red Rock Cabbage, old 



leaves 



Cowpeas 



Young tobacco leaves, 



2-12 cm. in length 



Old tobacco leaves, 20-40 



cm. in length 



Young tobacco leaves, 



2-12 cm. in length 



Old tobacco leaves, 20-40 



cm. in length 



June 11, '13 



June 11/13 



June 12/13 



June 12/1.3 



June 24,'13 



June 24,'13 



June 13,'13 



June 13/13 



June 14/13 



June 14/13 



July 1/13 



July 1/13 

 June 14/13 



July 12/13 

 July 12/13 

 July 12/13 

 July 12/13 



-4 



-4 



-4 



-4 



-3 



-3 



-5 



-5 



-3 



-3 



-4 



-4 

 -3 



-2 

 -2 



-2.5 

 -2.5 



18 

 40 

 12 

 17 

 32 

 30 

 10 



4 



3 



4 



5 



5 

 6 

 (plants) 



0.520 

 0.575 



Leaves all dead; stems 

 alive. Old and young 

 leaves equally injured. 

 Young stems dead ; old 

 stems alive. 



20.0 

 75.0 

 75.0 

 90.0 



In case of apples and peaches the young leaves are uniformly 

 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 the old 

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

 minations gave a depression of 1.931 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 density will explain the greater 



