502 



Journal of Agricultural Research 



Vol. XIII, No. lo 



A test comparing rye, wheat, and barley was conducted on March 8. 

 The leaves were collected at 4.30 p. m. They were treated with toluene 

 for about 16 hours, and the sap was kept on ice until the freezing point 

 was determined. The results are given in Table VII. 



Table VII. — Relative freezing point of the sap of winter cereals on March 8, igi6 



Here also no significant differences were observed. The barley showed 

 a greater depression than the rye, although much less able to survive low 

 temperatures. 



A fifth test compared wheat, barley, and oats grown in the greenhouse. 

 The leaves were from plants about 40 days old from planting. They were 

 watered several times before gathering, in order to insure a normal con- 

 dition with respect to turgidity. The leaves were treated with toluene 

 on ice for 16.5 hours, and the extracted sap was placed on ice until the 

 freezing point was determined. The results, which are presented in 

 Table VIII, show no large differences and apparently no relation between 

 depression of the freezing point and the ability of the different kinds of 

 grain to survive low temperatures. 



Table VIII. — Relative freezing point of the sap of winter cereals grown in the green- 

 house 



Kind of grain. 



Variety. 



Freezing point of sap after treat- 

 ment (°C.). 



Sample I. Sample 2. Average, 



Wheat 

 Barley 

 Oats. . 



Kanred 



Tennessee Winter 

 Culberson 



•I. 700 

 -I. 840 

 ■I-59S 



•I. 780 



■1-755 



— I. 700 

 -I. 810 

 -1.675 



Several determinations were made directly without extracting the sap. 

 This was done by wrapping the thermometer bulb with leaves, placing it 

 in the air chamber, and inserting the whole in the freezing mixture of 

 salt and ice, and proceeding in the usual way. This method appears to 

 have been used by Miiller-Thurgau and more recently by Bouyoucos 

 and McCool.* 



' BouYOXJCos, G. J., and McCoot, M. M. determination of cbll sap concentration by thb 

 PRB8ZINO POINT METHOD. In Jour. Amer.-Soc. Agron., v. 8, no. t, p. 50. 1916. 



