When a tree is damaged, it first leaks sap from the wound opening. In most cases, a callus quickly forms at the edges. This keeps the sap from oozing out. Cells in the cambium, or growth tissue, begin to multiply and grow inward. If the edges are jagged, the opening may never close completely.
Large wounds form permanent scars on the surface.
You can see these knots in the tree's bark. Procedure Find a rotting tree in a wooded area. Put on the plastic gloves. Use the trowel to move and uncover materials on the tree. Use the tweezers to collect items you want to inspect further and put these in the jar.