Note the shape of the typical cells. Locate the Stomata. The Stomatal Apparatus is composed of Guard Cells and the Stoma or opening. Subsidiary Cells may also be present. I use Stomata or Stomatal Apparatus to indicate the compliment of cells and the opening.
Some authors use a slightly different nomenclature.
Fuchsia epidermis with highly undulating cell walls and Guard Cells. Note the Chloroplasts in the Guard Cells. Epidermal cells have poorly differentiated plastids. However, the Guard Cells have chloroplasts which are important for stomatal functions. Higher magnification of Guard Cells from Fuchsia epidermis.