The basic parts of a tree are the roots, trunk, branches, twigs and leaves. Tree stems consist mainly of carry and transport tissues. Wood consists of xylem cells, and woof is made of phloem and other tissues outside to the vascular cambium.
Trees may be generally grouped into exogenous and endogenous trees according to the way in which their stem diameter increases. Exogenous trees, which include the great bulk of contemporary trees, grow by the addition of new wood outwards, right away under the bark. Endogenous trees, mostly in the monocotyledons, grow by addition of new material inwards.
As an exogenous tree grows, it creates growth rings. In temperate climates, these are usually visible due to changes in the rate of growth with heat variation over a yearly cycle. These rings can be counted to conclude the age of the tree, and used to date cores or even timber taken from trees in the past; this perform is known as the science of dendrochronology. In some humid regions with constant year-round weather, growth is continuous and different rings are not formed, so age resolve is impossible. Age willpower is also impossible in endogenous plants.