268 



POMOLOGY 



that a rapid fall of temperature near the freezing point is 

 more harmful than near the point at which the tissue is 

 killed and this fact is applied as a possible explanation of 

 "sun-scald" of apple trees. 



The following excerpts from Chandler's data illustrate 

 this: 



Table LXXXI 



the effect of slow and rapid lowering of temperature on the 

 killing of plant tissue 



Kind of buds 



Date 



Niwibcr 

 buds 



Percent, 

 killed 



Number 

 buds 



Percent, 

 killed 



Slowly to 

 —18° C. 



Rapidly to 

 —13.5° C. 



Rice's seedling peach 



Elberta peach 



Jonathan apple 



Montmorency cherry 

 Chabot plum 



Mar. 22 

 Mar. 22 

 Mar. 22 

 Mar. 22 

 Mar. 22 



138 

 100 

 34 

 176 

 236 



44.2 

 88.0 

 64.7 

 58.5 

 78.3 



154 

 85 

 33 

 184 

 183 



51.9 

 92.9 

 75.7 

 62.5 

 86.8 



When twigs of the apple, peach, cherry, and plum were 

 exposed to a temperature which gradually fell to — 18° C, 

 the killing was about the same as when it fell rapidly to 

 — 13.5° C. These with other data show conclusively that 

 both buds and wood are more surely injured if the tempera- 

 ture drops rapidly than slowly, even though it does not go 

 so low in the rapidly frozen tissues. 



237. Protection of bud scales. — It has usually been 

 assumed that the bud scales afford protection from cold as 

 well as prevent loss of moisture from or entrance of water 

 into the buds. However, this has not held true experi- 

 mentally ^ for buds which had their scales removed were 

 not frozen any quicker or at a higher temperature than were 

 1 Wiegand, K. M. Bot. Gaz., Vol. 41, pp. 373-424. 



