trees and retains its verdure. Our fruit-trees, which are all exotics,
retain their foliage long after our forest-trees are leafless; and if
we visit an arboretum in the latter part of October, we may select the
American from the foreign species, by observing that the latter are
still green, while the others are either entirely denuded, or in that
colored array which immediately precedes the fall of the leaf.
The exotics may likewise be distinguished in the spring by their
precocity,--their leaves being out a week or ten days earlier than the
leaves of our trees. Hence, if we take both the spring and autumn into
the account, the foreign, or rather the European species, show a period
of verdure of three or four weeks' greater duration than the American
species. Many of the former, like the Weeping Willow, do not lose
their verdure, nor shed their leaves, until the first wintry blasts of
November freeze them upon their branches and roll them into a crisp.

In a natural forest there is a very small proportion of perfectly formed
trees; and these occur only in such places as permit some individuals to
stand isolated from the rest, and to spread out their branches to their
full extent. When we walk in a forest, we observe several conditions
which are favorable to this full expansion of their forms. On the
borders of a pond or morass, or of an extensive quarry, the trees
extend their branches into the opening, but, as they are cramped on the
opposite side, they are only half developed. But this expansion takes
place on the side that is exposed to view: hence the incomparable beauty
of a wood on the borders of a pond, or on the banks of a river, as
viewed from the water; also of a wood on the outside of an islet in a
lake or river.

Fissures or cavities sometimes occur in a large rock, allowing
a solitary tree that has become rooted there to attain its full