1. Trees are
plants that survive year after year and have a single main stem composed
entirely of wood. Some kinds grow to only ten feet. Others attain heights of
more than 350 feet. These giants also have stems that are as much as 100 feet in
circumference (圆周). 2. Over 25,000 different species of tree
grow around the wood, except near the North and South Poles. They all belong to
one of two possible groups. They are either coniferous (松类的) or deciduous (落叶的).
Coniferous trees are evergreens (常绿的), such as pine or fir, which bear
needlelike foliage (叶子) all year long. Many deciduous trees have broad leaves,
which they usually shed each year at the beginning of the cold season.
3. Trees provide people with a host of oils, drugs, glues, candy, cloths,
fuels, and well over 10,000 wooden products. Some have unique qualities that
make their wood valuable for special purposes. One particular type of tree, for
example, is used to make fishing rods because it is not strong but unusually
flexible. Queensland walnut is used by the electrical industry in Australia,
because it is almost as good an electrical insulator as rubber. One of the world
most unusual trees is the teak (柚木). It is one of the heaviest of all woods, and
it has the largest leaves of any tree. These enormous leaves are two feet square
and their surface is so tough and coarse that cabinetmakers in India use them as
sandpaper. Teakwood itself is so heavy that when a teak tree is first cut down
it will not float in water. It takes three years for the ten or fifteen-ton
trunk to dry out enough so it will not sink. 4. Of all the
world's billions of living trees, the tallest is a giant redwood in California.
It towers 368 feet. This redwood tree is anchored and nourished by a massive
root system. It extends over three full acres.