Fern (Adiantum capillus-veneris) leaf. Light micrograph of a section through a leaf (horizontal) from a maidenhair fern, showing the sporangia (centre, round), within which spores are produced. Also seen are the upper epidermis (blue) with stomata (pores, green). Beneath this are the parenchyma cells of the palisade mesophyll (green-yellow), containing chloroplasts, and spongy mesophyll (yellow). Magnification: x37 when printed 10 centimetres wide.