part of leaf epidermis BTO:0000718 BrendaTissueOBO The blade consists of an upper and a lower layer of closely fitted epidermal cells, including specialized paired guard cells that control the size of tiny pores, or stomata, for gaseous exchange and the release of water vapor (see transpiration). The upper epidermis is usually coated with a waterproof cuticle and contains fewer stomata than the underside, if any at all. leaf lamina