March, 1922] JOHNSTON — UNDERCOOLING OF PEACH BUDS 
97 
25 was 13° F., while the undercooling in the laboratory on February 18 
was 18.1° F. for the Elberta buds. This temperature of 13° F. apparently 
did not injure the buds in the orchard at that stage of their development. 
The peach blossoms on the trees in this same orchard were, however, prac- 
tically all killed on March 29 and 30 by temperatures of 25° and 20° F. 
respectively. These higher temperatures came at a time when the buds 
were in a more tender condition. If the experiment here reported could 
have been continued, it would undoubtedly have shown a further rise in 
the undercooling graphs. 
Some of the buds from twigs cut on March 14 were dipped into water 
and then frozen while a thin film of water adhered to the bud-scales. These 
data and those of Greensboro buds sprayed and unsprayed are shown in 
table 2. Practically no difference is seen in either the undercooling or the 
Table 2. Data Showing the Undercooling and Freezing Point of Dry and Wet Buds, and oj 
Sprayed and Unsprayed Buds 
Condition 
of Buds 
Undercooling 
Freezing Point 
Elberta 
Greensboro 
Elberta 
Greensboro 
Dry 
Wet 
Sprayed 
Deg. F. 
22.5 
234 
Deg. F. 
19.9 
22.3 
20.1 
20.3 
Deg. F. 
25.0 
29-5 
Deg. F. 
25.2 
29-3 
24.8 
25.0 
Not sprayed 
freezing points of the sprayed and unsprayed Greensboro buds. The 
Greensboro tree used throughout this series of experiments had been 
sprayed with lime-sulphur solution on the day previous to this particular 
experiment. The unsprayed Greensboro was growing near by. Buds of 
both varieties show a greater undercooling when in the dry condition than 
when wet. Crystallization seemed to be more rapid and complete in the 
case of wet buds, as is indicated by the higher temperatures obtained in the 
freezing-point columns. These data obtained from dry and wet buds, 
although meager, indicate that wet buds freeze at a higher temperature 
than dry buds. This is in agreement with the results obtained by Harvey,^ 
and by Chandler^ who states that 
Tissue with a wet surface killed worse at a given temperature than did tissue with no 
moisture on the surface. 
West and Edlefsen^^ in their orchard experiments of 1912 likewise found 
that wet buds and blossoms were killed at low temperatures which did no 
injury to similar buds and blossoms in a dry condition. 
8 Harvey, R. B. Op. cit. 
^ Chandler, W. H. The killing of plant tissue by low temperature. Univ. Mo. Agr, 
Exp. Sta. Res. Bull. 8. 1913. 
10 West, F. L., and Edlefsen, N. E. Orchard heating. Utah Agr. Coll. Exp. Sta. Bull. 
161. 1917. 
