This piece of oak has literally turned into stone. The radial cut is also called quarter-sawed lumber because the log is actually cut into quarters. T he thick, outer layer of bark on a tree trunk is composed of suberized cork cells which contain a waxy, waterproof coating called suberin. The cork layer becomes deeply fissured as the trunk expands in girth. Special openings in the bark layer called lenticels allow for gas exchange.
Lenticels are very prominent in some stems.
The phloem layer is not destroyed, and the cork can be harvested repeatedly from the trees. In most trees, peeling off the bark will kill the tree because the vital phloem layer is also ripped away and destroyed. Removing a ring of bark from the trunk of a tree or shrub is called girdling. Cork is still the best stopper for perishable beverages, such as fine wines, because other synthetic polymers may affect the flavor and quality of the wine. For obvious reasons, bottle corks are generally cut at right angles to the lenticels.