The different layers of wood and bark are:
Xylem (Sapwood): Contains active xylem that transports water and dissolved nutrients
Xylem (Heartwood): Old xylem that no longer conducts fluid but helps support the tree.
Cork: Contains nonfunctioning phloem.
Cork Cambium: A meristem that produces the protective layer of cork.
Phloem: A vascular tissue that transports sugars made by photosynthesis.
Vascular Cambium: A meristem that produces new xylem and phloem, increasing stem width.