260 
PRUNING AND THINNING. 
[Part IV. 
but near artificial ponds or dams no growth 
whatever should be allowed : roots are the 
great creators of leaks. Nor should they be 
allowed on masonry. Koots, by turgescence, 
will rend apart the strongest masonry, or lift 
any weight of stone. In Greece, Italy, and 
throughout the East, roots are the great dilapi- 
dators of the ruins of antiquity. We may 
observe the effect of a too sudden exposure to 
the opposite force of drought in the warping 
and rending asunder of the strongest woody 
organisations. 
