Why are the epidermis layers of the leaf coated in a waxy cuticle

prevent excessive loss of water

Explanation:

The epidermis is a single layer of cells covering all plant organs. The epidermal cells are elongated in the direction of stem length and flattened. They have no chloroplast and their outer walls are covered by a waxy cuticle that prevents excessive loss of water through evaporation. The cuticle also protects the inner tissues from infection and mechanical injury.