tracheid

thumb|220px|In radial section, two tracheids of a coniferous wood species are shown. A series of bordered Pit (botany)|pits are also appearing in each tracheid. thumb|150px|A tracheid of oak shows pits along the walls. It has no perforation plates. Angiosperms have both tracheids and vessel elements.

A tracheid is a long and tapered lignified cell in the xylem of vascular plants. It is a type of conductive cell called a tracheary element. Angiosperms also use another type of conductive cell, called vessel elements, to transport water through the xylem. The main functions of tracheid cells are to transport water and inorganic salts, and to provide structural support for trees. There are often pits on the cell walls of tracheids, which allows for water flow between cells. Tracheids are dead at functional maturity and do not have a protoplast. The wood (softwood) of gymnosperms such as pines and other conifers is mainly composed of tracheids. Tracheids are also the main conductive cells in the primary xylem of ferns.