240 TIMBER AND SOME OF ITS DISEASES, [chap. 



Isles often begins to shoot at the end of March 

 or beginning of April, whereas in the mountains it 

 may be devoid of leaves in May. This is because 

 the transition from winter to spring is very sudden 

 on high slopes, whereas in the lowlands and valleys 

 it may be very gradual. The consequence is that 

 in the Alps, when the buds once begin to open 

 they do this rapidly and vigorously, and the tender 

 leaves and shoots are quickly formed and soon 

 harden beyond the reach of those late spring frosts 

 which do so much damage in our country : in the 

 lowlands, on the contrary, the leaves slowly develop 

 at a time when late frosts are very apt to recur 

 at night, and they are for several weeks exposed to 

 this danger ; and if a sharp frost does come, the 

 chances are that not only will the first output of 

 tender leaves be killed off, but the whole shoot 

 suffers, and frost-wounds are formed in the young 

 cortex. 



Another point comes into consideration also. 

 In warm damp valleys the whole tree is apt to be 

 more watery, and it is well known that the soft 

 tissues, like the cortex, suffer more from frost when 

 filled with watery sap, than do harder, drier, more 

 matured ones. It has been shown, according to 

 Sorauer, that dead patches, exactly like those which 



