tree
www.british-trees.com
www.wildlifesafari.info
http://homepages.ihug.co.nz/~crysalis
www.ecoworld.org/trees/ecoworld_trees_home.cfm
www.globalforestscience.org
Tree
Tree
A perennial woody plant at least 20 ft (6 m) in height at maturity, having an erect stem or trunk and a well-defined crown or leaf canopy. However, no sharp lines can be drawn between trees, shrubs, and lianas (woody vines). The essence of the tree form is relatively large size, long life, and a slow approach to reproductive maturity. The difficulty of transporting water, nutrients, and storage products over long distances and high into the air against the force of gravity is a common problem of large treelike plants and one that is not shared by shrubs or herbs.
Classification
Almost all existing trees belong to the seed plants (Spermatophyta). An exception are the giant tree ferns which were more prominent in the forests of the Devonian Period and today exist only in the moist tropical regions. The Spermatophyta are divided into the Pinophyta (gymnosperms) and the flowering plants, Magnoliophyta (angiosperms). The gymnosperms bear their seed naked on modified leaves, called scales, which are usually clustered into structures called cones—for example, pine cones. By contrast the seed of angiosperms is enclosed in a ripened ovary, the fruit. See Magnoliophyta, Pinophyta
The orders Cycadales, Ginkgoales, and Pinales of the Pinophyta contain trees. Ginkgo biloba, the ancient maidenhair tree, is the single present-day member of the Ginkgoales. The Cycadales, characteristic of dry tropical areas, contain many species which are small trees. The Pinales, found throughout the world, supply much of the wood, paper, and building products of commerce. They populate at least one-third of all existing forest and include the pines (Pinus), hemlocks (Tsuga), cedars (Cedrus), spruces (Picea), firs (Abies), cypress (Cupressus), larches (Larix), Douglas-fir (Pseudotsuga), sequoia (Sequoia), and other important genera. The Pinales are known in the lumber trade as softwoods and are popularly thought of as evergreens, although some (for example, larch and bald cypress) shed their leaves in the winter.
In contrast to the major orders of gymnosperms which contain only trees, many angiosperm families are herbaceous and include trees only as an exception. Only a few are exclusively arborescent. The major classes of the angiosperms are the Liliopsida (monocotyledons) and the Magnoliopsida (dicotyledons). The angiosperm trees, commonly thought of as broad-leaved and known as hardwoods in the lumber market, are dicotyledons. Examples of important genera are the oaks (Quercus), elms (Ulmus), maples (Acer), and poplars (Populus).
The Liliopsida contain few tree species, and these are never used for wood products, except in the round as posts. Examples of monocotyledonous families are the palms (Palmae), yucca (Liliaceae), bamboos (Bambusoideae), and bananas (Musaceae).
Morphology
The morphology of a tree is similar to that of other higher plants. Its major organs are the stem, or trunk and branches; the leaves; the roots; and the reproductive structures. Almost the entire bulk of a tree is nonliving. Of the trunk, branches, and roots, only the tips and a thin layer of cells just under the bark are alive. Growth occurs only in these meristematic tissues. Meristematic cells are undifferentiated and capable of repeated division. See Flower, Lateral meristem, Leaf, Root (botany), Stem
Growth
Height is a result of growth only in apical meristems at the very tips of the twigs. A nail driven into a tree will always remain at the same height, and a branch which originates from a bud at a given height will never rise higher. The crown of a tree ascends as a tree ages only by the production of new branches at the top and by the death and abscission of lower, older branches as they become progressively more shaded. New growing points originate from the division of the apical meristem and appear as buds in the axils of leaves. See Apical meristem, Bud, Plant growth
In the gymnosperms and the dicotyledonous angiosperms, growth in diameter occurs by division in only a single microscopic layer, three or four cells wide, which completely encircles and sheaths the tree. This lateral meristem is the cambium. It divides to produce xylem cells (wood) on the inside toward the core of the tree and phloem cells on the outside toward the bark. In trees of the temperate regions the growth of each year is seen in cross section as a ring. See Phloem, Xylem
Xylem elements become rigid through the thickening and modification of their cell wall material. The tubelike xylem cells transport water and nutrients from the root through the stem to the leaves. In time the xylem toward the center of the trunk becomes impregnated with various mineral and metabolic products, and it is no longer capable of conduction. This nonfunctional xylem is called heartwood and is recognizable in some stems by its dark color. The light-colored, functional outer layer of the xylem is the sapwood. See Wood anatomy
The phloem tissue transports dissolved carbohydrates and other metabolic products manufactured by the leaves throughout the stem and the roots. Most of the phloem cells are thin-walled and are eventually crushed between the bark and the cambium by the pressures generated in growth. The outer bark is dead and inelastic but the inner bark contains patches of cork cambium which produce new bark. As a tree increases in circumference, the old outer bark splits and fissures develop, resulting in the rough appearance characteristic of the trunks of most large trees.
In the monocotyledons the lateral cambium does not encircle a central core, and the vascular or conducting tissue is organized in bundles scattered throughout the stem. The trunk is not wood as generally conceived although it does in fact have secondary xylem. See Forest and forestry, Plant physiology, Plant taxonomy
What does it mean when you dream about trees?
The sobriquet “tree of knowledge” and the proverb “they shall be known by their fruits” reflect the ancient heritage of this archetypal dream symbol. The size and the condition of the tree may indicate how one views one’s inner strength and “growth” in the world.
tree
[trē]tree
(mathematics, data)Although maybe not part of the widest definition of a tree, a common constraint is that no node can have more than one parent. Moreover, for some applications, it is necessary to consider a node's daughter nodes to be an ordered list, instead of merely a set.
As a data structure in computer programs, trees are used in everything from B-trees in databases and file systems, to game trees in game theory, to syntax trees in a human or computer languages.
tree
(1) See forests and trees.(2) An external DOS/Windows command that displays a subfolder tree, as follows:
tree display hierarchy tree /f display files and subfolders
(3) A hierarchical structure that is conceptualized as an upside-down tree with the starting point at the top, which is the root. For example, in a company organization chart, the highest level is the executive office. The various divisions are the branches, and the departments are branches off the divisions.
The Folder Tree
The term often refers to the file/folder hierarchy on a hard disk. In Windows and Mac, the Explorer and Finder utilities are used to display these hierarchies respectively. See root.
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| Windows and Mac Trees |
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| Folder hierarchies are displayed from left to right. The highest folder in the Windows example (top) is Program Files, while the highest level in the Mac (bottom) is the Utilities folder. |
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| Windows and Mac Trees |
|---|
| Folder hierarchies are displayed from left to right. The highest folder in the Windows example (top) is Program Files, while the highest level in the Mac (bottom) is the Utilities folder. |
Tree
(dreams)Tree
a long-lived plant (usually not under 2 m in height) with perennial woody stems and roots. In trees, as distinguished from shrubs, the main stem—the trunk with its branches forming a crown—is always well defined. Almost all trees belong to one of two groups—conifers (of the gymnosperms) or dicotyledons (of the angiosperms). The trunk and branches of a tree consist of wood and bark. The type of branching in various species is distinctive and determines their appearance. In trees grown in plantings the trunk is tall and almost cylindrical, and the crown is small and high. Trees grown in open places have short, thick trunks that widen toward the base (tapering), and their crowns begin low. As a rule, the lumber of the former is considerably more valuable. Among the monocotyledons there are trees with trunks that are thin and hollow (bamboo), poorly branched (dracena), or unbranched but bearing large leaves in place of branches (palms).
The tallest trees are the sequoia, the Douglas fir, and the eucalyptus (up to 100-110 m); the thickest are the baobabs (up to 9 m in diameter); and the longest lived are the sequoia, baobab, and dragon tree, which may live to an age of 3,000-5,000 years.
V. N. VEKHOV