Crystals in vegetative and reproductive organs of Pinellia pedatisecta (Araceae) were systematically examined and their morphology and distribution were determined with light microscopy.(1)Crystals were found in every organ.Raphides were most common,but druses,crystal sand and styloids were also found.(2)Leaf contained a variety of crystal,including raphides,druses,crystal sand and styloids.Raphides were distributed primarily within the upper mesophyll,with only occasional raphides coming into focus lower in the leaf.Crystal sand and stellate druses were also common crystal type in leaves,and occasionally styloids were seen.(3)Bulbs had many raphides bundles,giant druses near their conducting tissue.Adventitious roots had highly irregular raphide bundles and rare giant druses.(4)Spathes contained raphides,druses and crystal sand.Raphides were distributed primarily within the upper and the lower mesophyll,while crystal sand was distributed primarily on the upper and the lower epidermis.(5)Raphide bundles were found in anther wall,aligned perpendicular to the surface.The pollen sacs contained only small druses.(6)Raphides were found in pericarp and seed capsule.Based on acid solubility,all crystals appeared to be composed of calcium oxalate.In light of these findings,we conclude that calcium oxalate crystals of all types play an important role in protecting the plants against herbivory.