Xylem consists of three different types of cells: Xylem parenchyma cells and xylem fiber cells, which simply provide structural support for the most important xylem cells, the tracheary elements (TE). The TE are completely dead at maturity, and act like pipes to allow water and dissolved minterals to flow through them. There are two types of tracheary elements: vessel elements and tracheids. Though they have some structural differences, these two types function in the same manner.