Besides the root and stem tips, another important growing region is soon established in the seedling. After a tree seedling emerges from the ground, the cambium layer begins to form. It is found between the wood and the bark.

The cambium layer makes the tree grow in girth. The cambium consists of a single layer of cells that retain their capacity to divide throughout the life of the tree. This single layer of cells has a peculiar property in that it gives origin both to the wood and to the bark. In the spring, when the cambium layer becomes active, it begins to split off rows of wood cells to the inside and rows of bark cells to the outside. Generally speaking, the bark part of the tree is much thinner than the woody part, or the stem. Bark continuously sloughs off, while the wood accumulates. In the soft inner bark, or bast, are formed sieve tubes, through which manufactured sugar dissolved in water flows from the foliage to storage tissues in stem and root.

Injuries to the cambium layer can be a serious threat to the health of the tree. The cambium layer of a tree and can be injured by mowers or other careless gardening around the base of the tree.

Possible misspellings:

• cambrian layer
• cambrium layer