Fern (Adiantum capillus-veneris) leaf. Light micrograph of a section through a leaf (diagonal) from a maidenhair fern, showing a sporangium (lower centre), within which spores are produced. Also seen are the upper epidermis (red), stomata (pores) and parenchyma cells of the spongy mesophyll (red). Magnification: x37 when printed 10 centimetres wide.