Darkfield illuminated polarised light micrograph of a transverse cross-section of an asparagus (Asparagus officinalis) stalk showing raphides and vascular bundles. Raphides are calcium oxalate crystals with needle-like projections. They are a defence mechanism against predators. Vascular bundles transport water and dissolved substances inside the plant and help support the stem. Magnification: x93 when printed 10 centimetres wide.