The outer portion of a woody stem is called ‘bark’. The main function of the bark is to protect the inner, delicate structures. It protects them from drying out and also from injuries. The bark is formed over the years.
Some of the outer portions become dry and die. Some of these dry pieces are shed or broken off as the tree grows larger and larger. In the palm tree, there is no clear separation between the bark and the wood.
Below Bark info from Wikipedia (Read More):-
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term.[1] It overlays the wood and consists of the inner bark and the outer bark. The inner bark, which in older stems is living tissue, includes the innermost area of the periderm. The outer bark in older stems, includes the dead tissue on the surface of the stems, along with parts of the innermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees is also called the rhytidome. Products used by people that are derived from bark include: spices and other flavorings, tannin, resin, latex, medicines, poisons, various hallucinatory chemicals and cork. Bark has been used to make cloths, canoes, ropes and used as a surface for paintings and map making;[2] A number of plants are also grown for their attractive or interesting bark colorations and surface textures.
http://en.wikipedia.org/wiki/Bark
