June 3, 1918 Density of Cell Sap and Winter Hardiness in Grain 503 



Owing to the time required to make readings, only two or three 

 varieties could be examined at one time. The data are presented in 

 Table IX. Each recorded reading is the average of several from the 

 same sample. 



Table IX. — Relative freezing point of the leaves of winter cereals 



Date of determination. 



Freezing point (°C.). 



Kharkof 

 wheat. 



Fultz 

 wheat. 



Rye. 



Barley. 



January 16, 191 7 

 January 19, 191 7 

 January 27, 191 7 



-3-47 



-2. 17 



-2. 06 



-3-56 



-3-58 



-2-39 



The depression of the freezing point determined in this way is somewhat 

 greater than for the extracted sap, but the differences between kinds of 

 grain are not consistent enough to certainly indicate a relation between 

 the freezing point of the sap and ability to resist cold. In two tests the 

 rye has a lower freezing point than either barley or wheat; but in a third 

 test, on January 27, Kharkof winter wheat showed a greater depression 

 than the rye. 



An attempt was made to obtain a measure of the accuracy of this 

 method by collecting four samples of winter wheat at the same time from 

 the same plot, and treating them identically. The freezing point of each 

 is shown in Table X. 



Table X. — Freezing point of duplicate samples of wheat determined by the direct method 



It will be seen that the variations are of the same order as those 

 observed in determinations of the extracted sap. 



Table XI summarizes the data from all tests. Since the depression 

 of the freezing points appears to depend so much on the balance the 

 plants are able to maintain between absorption and transpiration, it 

 would manifestly be unfair to include any tests but those in which the 

 leaves were secured under like conditions. Hence, the average includes 

 the first three tests only. 

 56112°— 18 3 



