Wood is the hard, dead tissue obtained from the trunks and branches of trees and shrubs. Woody tissue is also found in some herbaceous plants . Botanically, wood consists of xylem tissue which is responsible for the conduction of water around the plant. A living tree trunk is composed of (beginning from the center): the pith (remains of the primary growth); wood (xylem); cambium (a band of living cells that divide to produce new wood and phloem; phloem (conducting nutrients made in the leaves), and the bark. The wood nearest the cambium is called sapwood because it is capable of conducting water. However, the bulk of the wood is heartwood in which the xylem is impregnated with lignin which gives the cells extra strength but prevents them from conducting water. In temperate regions a tree's age can be found by counting its annual rings. Commercially, wood is divided into hardwood (from deciduous angiosperm trees) and softwood (from gymnosperms).