Orchid leaf. Light micrograph of a section through the leaf of an orchid (family Orchidaceae), showing leaf veins of vascular bundles running parallel through a cylindrical mass of ground tissue, mainly composed of spongy mesophyll parenchyma cells. Multiple needle-like crystals of calcium oxalate (brown) or calcium carbonate, known as raphides, can also be seen. Magnification: x4 when printed 10 centimetres wide.