What is the job of the waxy cuticle on the outside of a leaf?
Explanation
The waxy layer is waterproof, so it seals the broad flat surface against evaporation and keeps the leaf from drying out in the sun. It is not the barrier to gases that students imagine, because gases travel in and out through the pores of the surface rather than through the wax, and it neither shades the leaf nor soaks up rain.