Ciiap. IV.] 
MISCELLANEOUS. 
155 
they do not grow solely vertically downward 
like the tap-root of a seedling. In reference to 
an entire hill, of a given base, this increase of 
surface or space for the roots will be not only 
directly as the height of the hill, but also directly 
as the steepness of its sides. Taking one side of 
a hill, if the side forms an angle of forty-five 
degrees with the horizon, its additional surface 
or space for roots, as compared with its base, 
will be as the diagonal is to the side of a square. 
We are not to expect that trees drawn up in Effect of wind 
on trees. 
the interior of sheltered plantations, and trans¬ 
planted to exposed situations, will grow. If we 
could move a cube acre of ground, with a young 
tree, from a sheltered to an exposed situation, 
the plant would dwindle and decay. A tree 
grown in an exposed situation contrives by 
degrees to shelter itself; that is, it grows to 
leeward of itself. For the windward growth 
diverts the current of the wind, and throws it up. 
And we see, in exposed trees and woods, that 
they get taller by degrees from the windward to 
the leeward side. The chief injury which trees 
suffer from wind is while they are shooting. 
If the weather is calm while they are shooting, 
they will make a year’s growth upward and to 
windward. But their general growth will be 
