To the heart of the tree!
- The outer bark protects the tree from extreme temperatures, bad weather, insects and fungi. Very thin in birch trees, the outer bark may be one foot thick in the Douglas fir.
- The phloem (bast) is also called the inner bark. It conveys the food-bearing sap developed in the leaves down to the various parts of the tree.
- The cambium is a thin layer of cells which produce phloem on one side and sapwood on the other.
- Sapwood is the living wood in the tree through which the raw sap rises from the roots to the leaves.
- The heartwood consists of old cells. This is the dead part of the tree that nevertheless provides structural strength. If air could reach these cells, the heartwood would rot quickly.
- The pith is the central core of the tree.
