662 Journal of Agricultural Research vo1.xx.no. 8 



occasions, however, apples matured on branches that experienced 20 

 when the buds were in full bloom. 



(4) With Klberta peach buds in full bloom, 29 F. or above are the 

 safe temperatures, because even though occasionally 26 , 27 , and 28 do 

 no damage, yet on most occasions 28 will kill from one-fourth to one- 

 half. Twenty-six degrees kills about one-half of them and 22 ° about 

 nine-tenths. Temperatures as low as 18 have failed to kill all of them. 



(5) With sweet cherry buds in full bloom, 30 F. is the safe temperature ; 

 25 , 26 , 27 , 28 have done no damage; but 29 usually kills about one- 

 fifth. Twenty-five degrees usually kills about one-half, and when the 

 buds were showing color 22 killed only two-fifths of the buds. 



(6) Sour cherries are hardier than the sweet varieties. When the buds 

 were showing color 23 F. did not harm them, and when they were in full 

 bloom 26 killed but one-fifth and 22 only two-fifths of them. 



(7) With apricots, 29 F. is the safe temperature; 26 and 27 killed 

 about one-fifth and 22 killed one-half. They are fairly hardy, but they 

 bloom so early that they are frozen oftener than any of the other fruits 

 studied in the experiments. 



(8) The foregoing figures refer to the buds when in full bloom. Start- 

 ing from this stage, the earlier the stage of development the hardier the 

 buds are; and in general, when the fruit is setting the injury is from 5 to 

 10 per cent more than when they are in full bloom. 



(9) Sour cherries are the hardiest, and then follow in order apples, 

 peaches, apricots, and sweet cherries. 



(10) The fact that the same branch of buds will on one occasion ex- 

 perience 27 F. with 25 per cent injury and on another occasion take the 

 same temperature with no injury is no doubt due to the fact that the 

 juice is contained in capillary cells and supercooling results — that is, the 

 buds are cooled below the freezing point of the juice without the freez- 

 ing taking place. The great difficulty of killing all the buds even at 

 extremely low temperatures is due to the same cause together with the 

 fact that the cell sap may be very concentrated. Differences in the hardi- 

 ness of the different kinds of buds and also of the same buds at different 

 stages of development is due to differences in quality and concentration 

 of the cell sap. 



