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If it is surrounded
instead by an edging of shrub oaks, then you will probably have a
dense shrub oak thicket.

I have no time to go into details, but will say, in a word, that while
the wind is conveying the seeds of pines into hard woods and open
lands, the squirrels and other animals are conveying the seeds of oaks
and walnuts into the pine woods, and thus a rotation of crops is kept
up.

I affirmed this confidently many years ago, and an occasional
examination of dense pine woods confirmed me in my opinion. It has
long been known to observers that squirrels bury nuts in the ground,
but I am not aware that any one has thus accounted for the regular
succession of forests.

On the 24th of September, in 1857, as I was paddling down the Assabet,
in this town, I saw a red squirrel run along the bank under some
herbage, with something large in its mouth. It stopped near the foot
of a hemlock, within a couple of rods of me, and, hastily pawing a
hole with its fore feet, dropped its booty into it, covered it up, and
retreated part way up the trunk of the tree. As I approached the shore
to examine the deposit, the squirrel, descending part way, betrayed no
little anxiety about its treasure, and made two or three motions to
recover it before it finally retreated. Digging there, I found two
green pignuts joined together, with the thick husks on, buried about
an inch and a half under the reddish soil of decayed hemlock
leaves,--just the right depth to plant it. In short, this squirrel was
then engaged in accomplishing two objects, to wit, laying up a store
of winter food for itself, and planting a hickory wood for all
creation. If the squirrel was killed, or neglected its deposit, a
hickory would spring up. The nearest hickory tree was twenty rods
distant. These nuts were there still just fourteen days later, but
were gone when I looked again, November 21st, or six weeks later
still.

I have since examined more carefully several dense woods, which are
said to be, and are apparently, exclusively pine, and always with the
same result. For instance, I walked the same day to a small but very
dense and handsome white pine grove, about fifteen rods square, in the
east part of this town. The trees are large for Concord, being from
ten to twenty inches in diameter, and as exclusively pine as any wood
that I know.
Indeed, I selected this wood because I thought it the
least likely to contain anything else. It stands on an open plain or
pasture, except that it adjoins another small pine wood, which has a
few little oaks in it, on the southeast side. On every other side, it
was at least thirty rods from the nearest woods. Standing on the edge
of this grove and looking through it, for it is quite level and free
from underwood, for the most part bare, red-carpeted ground, you would
have said that there was not a hardwood tree in it, young or old. But
on looking carefully along over its floor I discovered, though it was
not till my eye had got used to the search, that, alternating with
thin ferns, and small blueberry bushes, there was, not merely here and
there, but as often as every five feet and with a degree of
regularity, a little oak, from three to twelve inches high, and in one
place I found a green acorn dropped by the base of a pine.

I confess I was surprised to find my theory so perfectly proved in
this case. One of the principal agents in this planting, the red
squirrels, were all the while curiously inspecting me, while I was
inspecting their plantation. Some of the little oaks had been browsed
by cows, which resorted to this wood for shade.

After seven or eight years, the hard woods evidently find such a
locality unfavorable to their growth, the pines being allowed to
stand. As an evidence of this, I observed a diseased red maple
twenty-five feet long, which had been recently prostrated, though it
was still covered with green leaves, the only maple in any position in
the wood.

But although these oaks almost invariably die if the pines are not cut
down, it is probable that they do better for a few years under their
shelter than they would anywhere else.

The very extensive and thorough experiments of the English have at
length led them to adopt a method of raising oaks almost precisely
like this which somewhat earlier had been adopted by Nature and her
squirrels here; they have simply rediscovered the value of pines as
nurses for oaks. The English experimenters seem, early and generally,
to have found out the importance of using trees of some kind as
nurse-plants for the young oaks. I quote from Loudon what he describes
as "the ultimatum on the subject of planting and sheltering
oaks,"--"an abstract of the practice adopted by the government
officers in the national forests" of England, prepared by Alexander
Milne.

At first some oaks had been planted by themselves, and others mixed
with Scotch pines; "but in all cases," says Mr. Milne, "where oaks
were planted actually among the pines and surrounded by them [though
the soil might be inferior], the oaks were found to be much the best.