WOUNDS 261 



of a similar character are also formed when branches drop from 

 trees naturally. 



As has been already stated, it sometimes happens that 

 parasitic fungi, especially species of Nectria, enter through 

 branch-wounds and produce cancerous diseases, which afterwards 

 spread in the stem. 



REMOVING DOUBLE LEADERS FROM THE SPRUCE 



When the spruce is grown in open lines in the nursery, it 

 tends to develop a double leader when about three or four years 

 old, so that instead of a single stem we find two. If one of the 

 two stems is not removed till the first thinning, the base dies and 

 decays exactly like the snag of a branch (Fig. 141), and becomes 

 enveloped more or less by the other stem. The wound-rot spreads 

 easily from the stump to the other stem, in which it may ascend 

 to the height of four feet. 



In order to avoid this injury, one of the shoots should be 

 removed in early life, as is easily done by means of a knife with 

 a long handle and a bent blade. In rare cases the technical 

 properties of the timber are reduced by a double leader again 

 forming in later life. Such an occurrence, however, happens 

 but seldom, and probably only when the tree occupies a very 

 open situation. 



Less damage is done by removing, during the first thinning, a 

 stem that has grown into another at the collar, as sometimes 

 happens in a very dense wood. Such cases of natural grafting 

 occur most frequently in woods that have been formed by 

 planting the young trees in bunches. Seeing that the stems are 

 separated by their cortex up to the twentieth or thirtieth year, 

 when the first thinning takes place, the coalescence is usually 

 only apparent, and the removal of one stem scarcely injures the 

 survivor. 



COPPICING 



When trees are cut over close to the ground, various 

 phenomena of regeneration which vary with species and age 

 make their appearance. Amongst conifers the Scotch pine 

 produces stool-shoots from dormant eyes only when very young. 



