Xylem – This tissue helps in the transport of water and dissolved substances throughout the plant. The different components of the xylem include tracheids, vessels, xylem parenchyma and xylem fibers. 1) Tracheids form the main conductive cells of some non-flowering plants. Water moves from the cell to cell through side walls. These cells are elongated cells with tapering ends. These cells with cell walls bear spiral, pitted or bordered-pitted thickenings.2) Vessels are advanced water conductive elements mostly seen in flowering plants. The cell walls are thickened with lignin. These provide rigidity and resistance to the cell wall and prevents it from collapsing during excess transpiration.3) Xylem parenchyma are the living cells of the xylem. They perform functions like secretion and storage.4) Xylem fibers are midway between tracheids and xylem parenchyma. They provide support to the plants.