why it was necessary that the earth should be clothed with vegetation
before animals could be introduced. A field-mouse dies and decays, and
its elements are appropriated by the roots around its grave; and we
can easily imagine the next generations of mice, the children and
grandchildren of the deceased rodent, feasting off the tender bark which
was made out of the remains of their parent. The soil of our gardens and
the atmosphere above it are full of potential tomatoes, beans, corn,
potatoes, and cabbages,--even of peaches of the finest flavor, and
grapes whose aroma is transporting.

Plants, as well as animals, have their peculiar tastes. Cut off the
supply of phosphate of lime from a field of corn, and it will not grow.
You can easily do this by planting the same land with corn for three
or four successive years, and your crop will dwindle away to nothing,
unless you supply the ground every year with as much of the mineral as
the corn takes away from it. All plants have the power of selecting from
the soil the materials necessary to their growth; and if they do not
find them in the soil, they will not grow. It is now a familiar fact,
that, when an old forest of deciduous trees has been felled, evergreens
will spring up in their places. The old oaks, hickories, and beeches,
as any observer would discover, pass their last years in repose, simply
putting out their leaves and bearing a little fruit every year, but
making hardly any new wood. An oak may attain to nearly its full size,
in spread of branches, in its first two hundred years, and live for five
or six hundred years longer in a state of comparative rest. It seems to
grow no more, simply because it has exhausted too much of the material
for its nourishment from the ground around its roots. At least, we know,
that, when we have cut it down, not oaks, but pines, will germinate
in the same soil,--pines, which, having other necessities and taking
somewhat different food, find a supply in the ground, untouched by