Final answer:
Dead cork cells replace the epidermis in the dermal tissue of woody stems and roots, forming a protective layer known as bark.
Step-by-step explanation:
In dermal tissue, dead cork cells replace the epidermis in woody stems and roots. Dermal tissue consists of the single-celled layer of epidermis which covers and protects underlying plant tissue. Over time, in woody plants, this epidermal tissue is replaced with a tougher protective layer known as bark, made primarily from cork cells. These cork cells are a part of the periderm, which becomes the external surface of the plant once the epidermis has been sloughed off. The bark acts as a significant protective barrier against physical damage and prevents water loss, while also serving for gas exchange through structures like lenticels.