In some, the leaves are needle-like and stomata are reduced in number and located in cavities on the epidermis. A layer of moist air builds up in the cavity. This reduces the humidity difference between the intercellular air spaces in the leaf and the immediate external environment thus reducing the rate of transpiration.
In some the epidermis of the leaves is multilayered and is covered with a thick waxy cuticle which reduces water loss through evaporation, e.g. oleander. The cuticle is normally shiny which helps to reflect solar radiation preventing the leaf from heating up rapidly.
