2 68 THE LARCH. 



a temporary check of growth, which it generally 

 regains next season. When, however, the tree be- 

 comes vitally diseased, insects attack not only the 

 foliage, but also the bark, and then the wood, and 

 ultimately terminate its existence, not by killing 

 it, but rather performing the functions of burial 

 according to nature's unerring laws. 



Fourth. The hazard of laying down one fixed un- 

 bending rule for thinning is almost as great as that 

 of recommending no thinning at all. There are, how- 

 ever, some general rules which may be laid down with 

 much certainty, definite objects being thereby sought 

 to be attained, such as, — 



A certain amount of air for the proper growth and 

 development of the tree ; therefore, thin to afford the 

 requisite amount. Light is also necessary, and there- 

 fore the rays of the sun must fall upon the foliage of 

 every branch, that it may be kept in perfect health and 

 vigour. The roots of the tree, as well as the branches, 

 must have room to spread — the former under ground, 

 the latter above it — so that food may be taken up for 

 nourishment, anchorage given to the stem, and proper 

 balance maintained amongst all its members. Trees 

 require different and often opposite kinds of treatment 

 at different stages of growth ; thus while young ones 

 require much light and a free circulation of air, 

 middle-aged and old ones require considerable shade 

 and moisture. Young trees, again, enjoy thinning, 

 while older ones dislike any disturbance or interference 

 of the kind. The roots of young trees are soft, spongy. 



