Xylem, one of the primary two variations of transport tissue in vascular(plants with lignified tissue)plants, constituted by tracheary cells : elongated cells responsible for both assisting in water and mineral transport while providing structural support which, possessing a lignified cell wall while at maturity being free of a living protoplasm(the nucleus and its ambient enzymes/materials, makes tracheids and vessel elements both hollow and dead at maturity)lacks any perforations(in contrast to the pore covered vessel elements),and vessel elements:type of xylem most prominently found in angiosperms, originating from the vascular cambium of thickening stems/secondary xylem, is responsible for the majority of water ferrying throughout the xylem to connected plant structures in that, although like tracheids hollow at maturity with lignified cell walls, their exclusively wielded perforations allow them to connect with other vessel elements. This creates continuous water-transporting vessels more efficient at transporting water/minerals. The two forces which act as the impetus for upward water movement are transpirational pull and root pressure. Transpirational pull is the creation of tension in the xylem as a result of evaporating water in the mesophyll creating menisci on the mesophyll cells cell walls, which forces xylem sap to rise. Root pressure is essentially the upward osmosis of water powered by a concentration gradient.The wood in the above picture is composed of xylem tissue(its consistency of course derived from the xylem cells lignified cell walls).