just fine,
*
But there's one more question. Why does
a
tree
need
a
trunk at all? Couldn't its crown grow
straight out of its roots?
A
tree needs a trunk so it can grow taller than
all the other plants around it, Otherwise it would
just be
a
bush. (Bushes don't have trunks.) Since
they're the tallest plants in the world, trees
don't need to be afraid of other plants. They can
grow above them all—except for other trees, of
course. [We'll find out later why there are some
anxious oaks out there.)
FIND
A
BIRCH
LOG.
If your family
buys
firewood,
it
will often
have
birch logs
in It—you can
recognize
them by their white
and
black
bark.
If
you
don't
have any firewood at home, ask your friends
who have fireplaces or fire pits.
Spread some dish detergent over one end of
the log. Now press your lips against the other
end
and
blow.
If
the
experiment works properly,
you'll see soap
bubbles
coming
out.
That happens
because the air you blow travels through the
water vessels in the wood until it reaches the
soapy film at the other end.
A tree is a trunk with branches and twigs on ft. Leaves or needles
grow on the twigs. But something really important is missing from this
description: the roots. They're the first part of a tree to grow.
AS SOON AS A SEED SPROUTS, a small root tip grows
down into the ground. It feels its way around to find
the best place to keep growing. (Roots like soft, loose,
damp soil the best.)
The
root spreads out and divides.
As the root divides, it grows fine hairs along its
length that increase its surface area so it can suck up
more water from the
soil.
These hairs dry out very
easily—that's why if
you
bring
a
baby tree home from
the nursery to plant
in
your
yard,
you have to be very
careful
not
to expose the roots to air for more
than
five
to ten minutes.
If the
roots are bare and not covered
in
soil,
the best thing is to wrap
a
plastic bag around
them until the hole for the tree is dug and you're
ready to plant it.
A
tree needs healthy roots if it is to
grow tall and strong.
Those cottony fungal threads I mentioned earlier
don't just grow around the root tips—they grow right
into the roots. This doesn't hurt the tree, though. In
fact, it's nice for the tree because it knows the fungi
are helping it. Not only do the fungi help the tree
suck
