INJURIOUS INFLUENCES 75 



removing the dead wood, which, if left, be- 

 comes a breeding ground for various boring 

 insects. When removing these dead branches 

 it is advisable to cut well back into the living 

 wood, which will induce the tree, if not too 

 far exhausted, to throw out fresh twigs and 

 foliage. 



Where larch and other poles become 

 " pumped " or hollow, it is a sure sign that 

 they are growing in unsuitable soil, and the 

 only remedy is to clear the crop and plant the 

 ground with trees that are more likely to 

 succeed. The larch usually becomes hollow- 

 stemmed when growing in gravelly soils rest- 

 ing on clay, while red-rot is most prevalent 

 with several species of pine and the silver fir 

 when they have been planted in soil that is 

 surcharged with moisture. The growth of 

 lichens on trees may also be accounted for by 

 excessive moisture in the soil. 



Young trees of the Spanish chestnut and 

 oak suffer from the effects of frost in the bark 

 becoming rent and exposing the timber to view. 

 It is caused by rapid shrinkage of the bark and 

 sapwood during frosty weather, and is most 



