Q.Student found a wooden stopper in lab. He was told by an old lab attendant that it is there for many years. He kept thinking how it did not rot?

As a stem's girth increases through the activity of the vascular cambium, the original epidermis is stretched until it ruptures and must be replaced. Cells of the outer cortex regain meristematic activity to form phellogen (cork cambium), a layer of thin-walled, actively dividing rectangular cells in the outer, extrastelar region of the stem. Like the vascular cambium, phellogen cuts cells off on both faces: outward-cut cells mature into suberised, water-impervious phellem (cork), and inward-cut cells mature into parenchymatous phelloderm (secondary cortex). Phellogen, phellem and phelloderm together make up the periderm. As the periderm develops, the pressure it creates crushes and kills the tissue outside it; bark is the informal term for everything external to the vascular cambium (crushed tissue, periderm and secondary phloem together), and is comparatively soft when formed early in a season and hard when formed late. Lenticels are raised, porous patches in the periderm where phellogen activity has been especially vigorous, and they allow gas and water-vapour exchange through the ot …