moisture from your breath will fog the glass.)
Larches ace one
of
just three conifers that turn yellow
in the fall and shed their needles
for
the winter.
*
If you
close your mouth, you won't suffocate, because
you can still breathe through your nose. When it's dry
outside and a tree shuts its many mouths, it doesn't
suffocate either, because it can still take in air through
its bark and roots,
The upper surface of
the
leaves has
a
waxy coating,
which often makes them shiny. The sun shines on the
tops of the leaves, and because the leaves are so
thin,
they can easily dry out. The wax makes them
thicker so they can hold in moisture, and this keeps
them healthy.
The leaves of each species of tree look different.
Hornbeam leaves, for example, have notched edges
like a saw. Others—such as oak leaves—have wavy
edges.
There's also a big difference between deciduous
trees and conifers. Deciduous trees have big, flat
leaves, The leaves of conifers are narrow and pointed,
like needles—and they
can
prick
you.
This is how coni-
fers protect themselves so that deer won't eat them.
In the winter, deciduous trees drop their leaves,
but conifers hold onto their needles. They do this
because many of them live where it's very
cold.
The
winters are long and the summers are very short. So
it's better for the trees to stay green the whole time,
That way they can start to make sugar whenever a
warm day arrives. If they had to wait to grow new
leaves first, summer would be over before they had
time to make any
food.
Flat leaves are very sensitive, and they really don't
like cold weather. The leaves of deciduous trees such
as oak and beech would freeze on the first frosty day.
That's why these trees drop their leaves before winter.
The needles of spruce trees and other conifers contain
oil that protects them from freezing.
*
But there are a few conifers that behave like decidu-
ous trees: the larch, the dawn redwood, and the bald
cypress. In the
fall,
their needles turn yellow and fall
off. That's why a lot of people think these trees are
dead when they see them in winter.
Really, they're just sleeping
through the cold time
of year.
TREES
LIVE
IN
MANY
DIFFERENT
environments–
dry or wet. hot or cold–ond the shape and
size of their leaves
is
important.
In
tropical rain
forests, large leaves with pointed tips shed
water easily when it rains. In desert regions,
feathery leaflets with a small surface area
lose moisture slowly in the hot sun.
HOW TREES WORK
Leaves Large
and Small
This
is
what tree mouths look
like
under
a
microscope.
Leaves are very important to trees, because trees use their
leaves to make their food. When trees are hungry–and they're
always hungry–they just hold their leaves up to the light.
LEAVES
MIX
WATER
WITH
