June 3. 1918 Density of Cell Sap and Winter Hardiness in Grain 501 



Table V. — Relative freezing point of the sap of winter cereals on December 77, jp/e 



As before, there seems to be little relation between the freezing point 

 of the sap and the known ability of the different cereals to survive se- 

 vere winters. The greatest depression is recorded for Culberson oats 

 and the least for Kharkof wheat. 



This may be explained by assuming that the oats are less able to se- 

 cure sufficient water to supply that lost by transpiration. Hence, the 

 water content of the tissue would be low and the cyroscopic value of the 

 extracted sap high. 



A third determination was made on January lo, 191 6. The leaves 

 were gathered at 8.30 a. m. The day was cool and cloudy. The soil 

 was wet, but not frozen. The plants appeared to be turgid. The leaves 

 were treated for 22.5 hours with toluene on ice (temperature 3° C), 

 allowed to stand exposed to the air for ten minutes to permit the excess 

 of toluene vapor to leave the tissue, and then expressed. The sap was 

 kept on ice at a temperature of about i .0° C. until January 1 1 , when the 

 freezing point was determined. The results are given in Table VI. 



Table VI. — Relative freezing point of the sap of winter cereals on fanuary 10, igi6 



Kind of grain. 



Variety. 



Freezing point of sap after treat- 

 ment (°C.). 



Sample i . Sample 2 



Average. 



Rye... 

 Wheat.. 



Do. 

 Barley. 

 Oats. . . 



Do. 



Ttu-key 



Fultz 



Tennessee Winter. 



Winter Turf 



Culberson 



■1.450 

 ■I. 360 

 ■1.390 

 ■ -970 



■1-385 

 ■1.540 



-I. 510 

 -1.440 

 -1.390 



-1-525 

 -1.380 



-1.450 

 -1-435 

 -1-415 

 -I. 180 



-I- 455 

 — I. 460 



In this case also there appears to be little if any relation between the 

 freezing point of the sap and winter hardiness. In fact, with the excep- 

 tion of the barley, the freezing point of all is about the same. There is 

 only CO! degree difference in the freezing point of the sap of rye, which 

 is the hardiest of the cereal grains, and of Culberson oats, which is the 

 least hardy. 



