A plant, sometimes called the tree of life, belonging to the genus Thuja of the order Pinales. It is characterized by flattened branchlets with two types of scalelike leaves. At the edges of the branchlets the leaves may be keeled or rounded; on the upper and lower surfaces they are flat, and often have resin glands. The cones, about ½ in. (1.2 cm) long, have the scales attached to a central axis (see illus.).