bark

Bark of a white oak

General term for the outer protective covering of the stems of woody plants. It consists of several layers, including the secondary phloem, cork cambium, and cork. The last of these, which is waxy and waterproof, is the thickest and hardens into the tough, fissured outer cating.

The bark is impervious to water and protects the stem from excessive evaporation; it also protects the more delicate tissues within. Lenticels (pores) in the bark allow gas exchange between the stem and the atmosphere. Extracts of bark may have medicinal uses, e.g., quinine from chinchona bark.

Related category

• BOTANY

Also on this site:

Encyclopedia of Alternative Energy & Sustainable Living
Encyclopedia of History

BACK TO TOP