206 



MASS. EXPERIMENT STATION BULLETIN 170. 



Winterkilling of Cork Cambium. 



\s already stated, the effects of low temperature on a tree may be en- 

 tirely local; i.e., it may affect some particular organ or some one portion 



95 



90 



85 



80 ' 



75 



70 



65 



40*60* 

 5CT 

 20* 

 10* 

 0* 



r 



U 



Li 



L 



U 



n 



u 



305.., 

 50.0 Lf 

 29.5 



29.0m 



35 

 50 

 25 



20 

 15 

 iO 

 5 

 x 4 



U / U L_. 



n 



_T 



ME AN RE L HUMIDITY 



^EAN TEMP 



---BAROMETER 

 FROST CRACK 



Fiu. 79. Showing curve of opening and closing of frost cracks in elm trees. The 

 lower curve represents the variations in the opening and closing the others 

 represent the mean relative humidity, mean temperature and barometer in 

 the order named. 



of the tree only. Following one of our extremely severe winters a few 

 years ago, elms and some sycamores were found suddenly discarding 

 their outer bark, a rather unusual phenomenon. This loss of the outer 



