Abstract:The morphology and distribution of calcium oxalate crystals in the vegetative organs of Colocasia esculenta (Araceae) were investigated by hand section under light microscope,and their chemical comstituents were identified by chemical methods. The results showed that the crystals were calcium oxalate crystals which could be divided into two types: needle and cluster crystals. There were three types of rhaphide idioblasts, such as biforines (exist in leaf, petiole and tuber), giant rhaphide bundles (exist in leaf, petiole, tuber and tuber bark), and tubular idioblast with abundant of rhaphides (only exist in adventitious root). The calcium oxalate rhaphides also scatter in tuber and adventitious root. Calcium oxalate druses crystals distribute in leaf, petiole, tuber, tuber bark and adventitious root, and the druses crystals in leaf, petiole and tuber bark were sharper than those in tuber and adventitious root. These calcium oxalate crystals in the vegetative organs of C. esculenta could be used as a defensive mechanism to prevent animal feeding.