Figure 1.

The cork layer of Quercus suber. (a) Virgin cork. This cork oak has never been debarked is still displaying its first cork layer. (b,c) Different quality types of amadia cork. (b) Cork plank thick enough and with very few discontinuities allowing stopper punching (red dots circle). It is possible to distinguish the growth rings (black arrow). (c) Example of a reduced-quality cork plank, thin in thickness and intersected by numerous lenticular channels (black arrowhead). White arrows indicate the growth direction from the surface in contact with the trunk and where the phellogen is (also known as cork belly) towards the surface in contact with the environment. In—cork plant inside; out—outermost cork plank surface.