Anatomically, there are three types of leaves :
(1) Dorsoventral : The leaves are horizontal in orientation with distinct upper and lower surfaces,The upper surface is called adaxial and lower surface is called abaxial surface. These are present in dicot plants only.
(2) Isobilateral: The leaf is placed in such a way that both its surface recieves equal amount of sunlight. A distinction into upper and lower surfaces is absent.These are found in monocot plants only.
(3) Unifacial: The leaves are generally cylindrical and a distinction into upper and lower surface is absent.e.g., Allium.