from the leaves. Veins also provide the
strong support that gives a leaf its shape.
The veins of broad leaves usually form a
netlike pattern throughout the leaf. Narrow
leaves usually have veins that lie
parallel to each other.
Different types of leaves may be
rounded, oval, spear shaped, heart
shaped, or triangular. Some leaves look
almost like fingers on a hand. Others
are shaped like needles. Some leaves
have smooth edges. Other leaves have
tiny points, called teeth. Leaves may
also have waxy or hairy coverings for
protection.
Photosynthesis
Inside all leaves are substances called
pigments, which give leaves their colors.
Green leaves get their color from a green
pigment called chlorophyll. Chlorophyll
helps with the job of photosynthesis. It
absorbs energy from sunlight. The leaves
use this energy to make sugars, which
are food for the plant.
Falling Leaves
Plants lose leaves and grow new ones
throughout their lives. But many trees,
called deciduous trees, shed all their
leaves during cold or dry seasons. Trees
Most plants
twist and bend
their leaves to
face the sun.
This helps
them absorb
more sunlight.
Leaves come in many different shapes. They may grow in several different arrangements.
118 Leaf BRITANNICA STUDENT ENCYCLOPEDIA
do this because they stop growing during
these times.
In autumn or during a dry season, the
leaves of deciduous trees lose their
chlorophyll. As the leaves’ green color
fades, red, yellow, or orange pigments
become visible. Meanwhile, a weak
layer of cells develops at the base of
each leaf’s petiole. This weak layer
causes the leaf to loosen and then fall
off. The leaves grow back when the
seasons change again.
#More to explore
Photosynthesis • Plant • Tree
League of
Nations
The countries that won World War I
(1914–18) set up an organization called
the League of Nations. They wanted
the League to be a place where
countries could settle disagreements by
talking instead of fighting. However,
the League was not strong enough to
keep World War II from breaking out
in 1939.
The first meeting of the League of
Nations was held in Geneva, Switzerland,
in 1920. Representatives from 42
countries attended. More than 20 other
countries joined later. U.S. President
WoodrowWilson wanted the United
States to join the League, but the U.S.
Congress disagreed. The United States
never joined.
The League’s goal was to prevent wars.
The member countries agreed to discuss
with the League any dispute that might
lead to war. The members also agreed to
act together against a country that was
making trouble. In addition, the League
tried to get countries to reduce their
number of weapons.
In the 1920s the League settled several
disputes between nations. In the 1930s,
however, the League faced new challenges.
Japan, Italy, and Germany
invaded other countries. The League
could not stop them. The invasions led
to WorldWar II.
The League’s failure to prevent the war
showed how weak it had become. The
League did not meet during the war.
After the war, in 1946, it was replaced
by a new organization, the United
Nations.
#More to explore
United Nations •Wilson,Woodrow
•WorldWar I
Representatives from many countries attend
a League of Nations meeting in about 1930.
BRITANNICA STUDENT ENCYCLOPEDIA League of Nations 119
Lebanon
The Middle Eastern nation of Lebanon
lies on the eastern shore of the Mediterranean
Sea. Lebanon has a large population
for its small area. Problems between
its Muslim and Christian people led to a
long civil war that lasted from 1975 to
1991. Lebanon’s capital and largest city
is Beirut.
Geography
Lebanon borders Israel and Syria. Along
the Mediterranean coast is a narrow
plain. The Lebanon Mountains, which
rise to 9,800 feet (3,000 meters), run
down the middle of the country. The
Anti-Lebanon Mountains form Lebanon’s
border with Syria. Between the
two mountain ranges lies the high, fertile
Bekaa Valley. The valley receives
water from the Litani, the only river in
Lebanon that flows throughout the year.
Lebanon’s coast has warm, dry summers
and mild, rainy winters. Summers in the
Bekaa Valley are hot and dry, and winters
are cool. Lebanon receives more rain
than most Middle Eastern countries.
Plants and Animals
Lebanon was once heavily forested. But
loggers cut down many trees over thousands
of years. Today forests cover about
8 percent of the land. Among Lebanon’s
plants are brush and low trees, including
oaks, pines, cypresses, firs, and junipers.
Lebanon is famous for its cedar trees,
but today they grow only in protected
mountain groves.
Lebanon’s animals include deer, wildcats,
hedgehogs, squirrels, martens
(small weasel-like mammals), and hares.
Flamingos, pelicans, cuckoos, and various
birds of prey also live there.
The city of Sidon, Lebanon, lies on the coast
of the Mediterranean Sea. Christian knights
built castles in Sidon in the 1200s.
120 Lebanon BRITANNICA STUDENT ENCYCLOPEDIA
People
Most Lebanese are Arabs. There are
small groups of Armenians and Kurds.
Arabic is the main language, but many
people speak English and French. Muslims
make up more than half of the
population. Most of the rest of the
