tree
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Ash is the name given to a few northern European trees and shrubs of the Fraxinus genus. They belong to the same family as the olive, lilac, and jasmine. Ashes generally have a compound leaf with leaflets arranged on either side of a stem and a winged fruit.
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The monkey-puzzle tree has a regular dome-shaped crown of downwards-pointing branches set with pointed leaves. Its name derives from the belief that monkeys have difficulty climbing it. It is the nearest living example of the trees of the Carboniferous period, about 300 million years ago, which gave us our coal.
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The mountain ash, or rowan, is native to Europe and West Asia. The tree has divided leaves with small toothed leaflets and red berries and grows to a height of 18 m/60 ft.
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The mass of flowers that appear on the branches of fruit trees in spring, before the growth of new leaves, is known as blossom. Apple blossom ranges in colour from white to dark pink and appears in mid to late spring.
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Tule tree, Oaxaca, Mexico. These massive trees can live up to 2,000 years. Of the eight tule trees in this locality, the one known as El Arbol del Tule (pictured) is the oldest and largest, with a circumference of about 54 m/177 ft. The tule trees are a unique natural monument; however, the lack of subterranean water and the increasing urbanization of the area seriously threatens their future.
Perennial plant with a woody stem, usually a single stem (trunk), made up of wood and protected by an outer layer of bark. It absorbs water through a root system. There is no clear dividing line between shrubs and trees, but sometimes a minimum achievable height of 6 m/20 ft is used to define a tree.
Angiosperms
A treelike form has evolved independently many times in different groups of plants. Among the angiosperms, or flowering plants, most trees are dicotyledons. This group includes trees such as oak, beech, ash, chestnut, lime, and maple, and they are often referred to as broad-leaved trees because their leaves are broader than those of conifers, such as pine and spruce. In temperate regions angiosperm trees are mostly deciduous (that is, they lose their leaves in winter), but in the tropics most angiosperm trees are evergreen. There are fewer trees among the monocotyledons, but the palms and bamboos (some of which are treelike) belong to this group.Gymnosperms
The gymnosperms include many trees and they are classified into four orders: Cycadales (including cycads and sago palms), Coniferales (the conifers), Ginkgoales (including only one living species, the ginkgo, or maidenhair tree), and Taxales (including yews). Apart from the ginkgo and the larches (conifers), most gymnosperm trees are evergreen.Tree ferns
There are also a few living trees in the pteridophyte group, known as tree ferns. In the swamp forests of the Carboniferous era, 300 million years ago, there were giant treelike horsetails and club mosses in addition to the tree ferns.Oldest trees
The world's oldest living trees are found in the Pacific forest of North America, some more than 2,000 years old.Conservation
According to a 1998 report by the World Conservation Monitoring Centre (WCMC) and the World Conservation Union, approximately 8,750 tree species (around 10% of all known tree species) are in danger of extinction. In the 20th century 77 species became extinct and 7 more species were reduced to fewer than a dozen specimens.How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content.
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