160 THINNING. 



is of but little importance, since it is certain they are 

 influenced in other ways namely, mechanically and 

 chemically. That thinning injuriously affects trees 

 both ways there is little or no doubt ; and we shall 

 first see how they are injured mechanically. When 

 two trees grow near each other, the branches on the 

 confronting sides are less developed than on the oppo- 

 site sides, and the roots underneath are developed in 

 a corresponding manner ; and if one of the trees is 

 removed by thinning, the whole of the weak side of 

 the remaining tree is exposed suddenly, and the wind 

 acting upon it strains the tender and weak roots to 

 such an extent as often to uproot the tree altogether. 

 But apart from actually uprooting and blowing over 

 the tree, the roots are strained and fractured so severely 

 that they lose their vitality. Any injury inflicted upon 

 resinous trees especially, whether upon branch, stem, 

 or root, is succeeded by an accumulation of resin ; and 

 this, when it occurs extensively to the roots, is fatal 

 to them, as it obstructs the sap-vessels and stops the 

 circulation. 



From observing the sickly aspect of a very exten- 

 sive plantation after being thinned, and being called 

 upon to assign a cause for it, which I was at the time 

 quite unable to do, I afterwards turned my attention 

 exclusively to the subject, and, after much labour, 

 concluded I had solved the problem. The plantation 

 consisted principally of Scots pine, with a small 

 mixture of larch, spruce, and some hardwoods. 



All species of trees did not present the same sickly 

 appearance, nor did the same species on all the different 

 situations and soils of the plantation. 



The Scots pine was, of all others, the most sickly, 

 especially upon the hard gravelly soils, and the larch 



