No More Learning

Surely it is not wonderful that cherry trees of all
kinds are widely dispersed, since their fruit is well known to be the
favorite food of various birds. Many kinds are called bird cherries,
and they appropriate many more kinds, which are not so called. Eating
cherries is a bird-like employment, and unless we disperse the seeds
occasionally, as they do, I shall think that the birds have the best
right to them. See how artfully the seed of a cherry is placed in
order that a bird may be compelled to transport it,--in the very midst
of a tempting pericarp, so that the creature that would devour this
must commonly take the stone also into its mouth or bill. If you ever
ate a cherry, and did not make two bites of it, you must have
perceived it,--right in the centre of the luscious morsel, a large
earthy residuum left on the tongue. We thus take into our mouths
cherry-stones as big as peas, a dozen at once, for Nature can persuade
us to do almost anything when she would compass her ends. Some wild
men and children instinctively swallow these, as the birds do when in
a hurry, it being the shortest way to get rid of them. Thus, though
these seeds are not provided with vegetable wings, Nature has impelled
the thrush tribe to take them into their bills and fly away with them;
and they are winged in another sense, and more effectually than the
seeds of pines, for these are carried even against the wind. The
consequence is, that cherry trees grow not only here but there. The
same is true of a great many other seeds.

But to come to the observation which suggested these remarks. As I
have said, I suspect that I can throw some light on the fact that when
hereabouts a dense pine wood is cut down, oaks and other hard woods
may at once take its place. I have got only to show that the acorns
and nuts, provided they are grown in the neighborhood, are regularly
planted in such woods; for I assert that if an oak tree has not grown
within ten miles, and man has not carried acorns thither, then an oak
wood will not spring up _at once_, when a pine wood is cut down.

Apparently, there were only pines there before. They are cut off, and
after a year or two you see oaks and other hard woods springing up
there, with scarcely a pine amid them, and the wonder commonly is, how
the seed could have lain in the ground so long without decaying.
But
the truth is, that it has not lain in the ground so long, but is
regularly planted each year by various quadrupeds and birds.

In this neighborhood, where oaks and pines are about equally
dispersed, if you look through the thickest pine wood, even the
seemingly unmixed pitch pine ones, you will commonly detect many
little oaks, birches, and other hard woods, sprung from seeds carried
into the thicket by squirrels and other animals, and also blown
thither, but which are overshadowed and choked by the pines. The
denser the evergreen wood, the more likely it is to be well planted
with these seeds, because the planters incline to resort with their
forage to the closest covert. They also carry it into birch and other
woods. This planting is carried on annually, and the oldest seedlings
annually die; but when the pines are cleared off, the oaks, having got
just the start they want, and now secured favorable conditions,
immediately spring up to trees.

The shade of a dense pine wood is more unfavorable to the springing up
of pines of the same species than of oaks within it, though the former
may come up abundantly when the pines are cut, if there chance to be
sound seed in the ground.

But when you cut off a lot of hard wood, very often the little pines
mixed with it have a similar start, for the squirrels have carried off
the nuts to the pines, and not to the more open wood, and they
commonly make pretty clean work of it; and moreover, if the wood was
old, the sprouts will be feeble or entirely fail; to say nothing about
the soil being, in a measure, exhausted for this kind of crop.

If a pine wood is surrounded by a white oak one chiefly, white oaks
may be expected to succeed when the pines are cut. 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.