Skip to main content Skip to Search Box
Summary Article: wood
from The Columbia Encyclopedia

botanically, the xylem tissue that forms the bulk of the stem of a woody plant. Xylem conducts sap upward from the roots to the leaves, stores food in the form of complex carbohydrates, and provides support; it is made up of various types of cells specialized for each of these purposes. Among them are tracheids, elongated conduction and support cells; parenchyma (food storage) cells, some of which form rays for transverse conduction; xylem vessels, formed of hollow cells joined end to end; and fiber cells that reinforce these tubes. In the conifers the xylem is made up mainly of tracheids, thus presenting a uniform, nonporous appearance; their wood is called softwood. Deciduous trees have more complex xylem, permeated by vessels, and are called hardwoods, although the description is sometimes inaccurate.

Commercial Uses

Freshly cut wood contains much moisture and tends to warp and split as it dries. Lumber is therefore seasoned before use—dried either slowly in the sun and air or more quickly by artificial means (kiln drying). Seasoning increases wood's buoyancy, strength, elasticity, and durability. Although synthetic materials have supplanted wood in many of its former uses, it is still widely employed for furniture, floors, railway ties, paper manufacture, and innumerable other purposes. Wood distillation yields methyl alcohol, wood tar, acetic acid, acetone, and turpentine; charcoal is made by burning or heating wood in insufficient air to consume it.

The wood of different species of trees varies considerably in weight, strength, and appearance. Softwood is normally uniform in grain (texture) and color; hardwood, in which the rays are more prominent and the arrangement of tissues is variable, produces lumber in which the grain may run vertically or horizontally and be coarse or smooth. The manner in which a log is cut results in lumber with thin or wide ray markings. A log cut horizontally shows the concentric annual rings; lengthwise cuts through the center are marked by thin vertical ray lines; and lengthwise cuts through the outer sections show the wood's characteristic wavy grain and wider ray markings, prized for their beauty. The rarer decorative woods may be cut in thin layers and glued to other wood structures (see veneer). Plywood, made of thin layers of wood glued so that the grains alternate in direction, makes an especially strong construction material. For some applications composition board offers another inexpensive substitute. The more recently developed cross-laminated timber is used to prefabricate entire walls or large sections of ceiling and floor. Pressure-treated wood is lumber that has had a preservative forced into it under pressure.

Bibliography
  • See Cone, H., Wood Structure and Identification (1979).
  • Bucksh, H., Dictionary of Wood and Woodworking Practice (2 vol., 1986).
The Columbia Encyclopedia, © Columbia University Press 2017

Related Articles


Full text Article Wood
Miller's Antiques Encyclopedia

Although plastic and synthetic materials were very fashionable from the late 1950s, designers, especially those in Scandinavia, continued to...

Full text Article wood
Word Origins

[OE] (Old English) The ancestral meaning of wood is probably ‘collection of trees, forest’; ‘tree’ (now obsolete) and ‘substance from which...

Full text Article wood
Philip's Encyclopedia

Hard substance that forms the trunks of trees; it is the xylem which comprises the bulk of the stems and roots, supporting the plant. Wood...

See more from Credo