The cellulosic outer layer or cortex of trees and other woody plants. The bark of certain species such as oak, hemlock, etc., is a source of tannic acid; medicinal products, e.g., quercitrin and quillaja, are also derived from barks, especially cinchona, from which quinine is obtained. Phenolicrich bark extracts mixed with epichlorohydrin are reported useful as adhesive compounds. An unusual form of bark is cork from the oak species Quercus suber. In the pulp industry, bark is removed from logs with high-pressure jets of water.
