Sage leaf. Coloured scanning electron micrograph (SEM) of a freeze-fracture through the mid rib of a sage leaf (Salvia officinalis). The large central vascular bundle has contains xylem surrounded by phloem. Smaller vascular bundles are also visible. Below the upper epidermis and surrounding the vascular bundles is a layer of palisade parenchyma cells containing chloroplasts. Beneath this layer is the spongy mesophyll which has large intracellular spaces for gaseous exchange. At the bottom is the lower epidermis, a single layer of closely packed cells where the stomata control gas exchange within the spongy mesophyll. Sage leaves are used in cooking and herbal medicine. Magnification: x35 when printed 10 cm wide.