How a Tree works.

1. The Bark is the tree's protection from the outside world. It keeps moisture out during rain, prevents loss of moisture when the air is dry, insulates against cold and heat, and wards off insects.
2. The Bast is the pipeline through which the food (Elaborated Sap) produced in the leaves is passed down to the tree. It lives for only a short time then dies and turns to Bark.
3. The Cambium layer is the growing part of the tree trunk. It annually produces new Sapwood on the inside and some Bast on the outside.
4. Sapwood is the tree's pipeline for moving water and minerals up the tree trunk to the leaves. Sapwood is new wood; as newer rings of Sapwood are produced, its inner cells lose their vitality and turn into Heartwood.
5. Heartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are intact.