tracheid One of the long, cylindrical, tapered cells in a trachea. The cell is dead and the wall has bands of lignin in it which add structural strength. Its function is to form part of the trachea and so to conduct xylem fluids.

tracheid A type of cell occurring within the xylem of conifers, ferns, and related plants. Tracheids are elongated and their walls are usually extensively thickened by deposits of lignin. Water flows from one tracheid to another through unthickened regions (pits) in the cell walls. Compare vessel element.