The stomatal pore, guard cell, the subsidiary and epidermal cell are all together known as stomatal apparatus. The stomata are the opening found in the epidermis of leaves which is capable of regulating the transpiration and gaseous exchange. The stomatal pore is surrounded by two specialized epidermal cells which are known as guard cells. These guard cells are kidney shaped in dicot and dumbel shaped in monocots. The epidermal cells surrounding the guard cells are specialized and are known as subsidiary cells or accessory cells.