botany, a genus of the decandria monogynia clas. The calyx consists of five leaves; the petals are five; and the antherae are rolled and barren; the pod is a legumen. There are 30 species, all natives of warm climates. The cassia fistula is a native of Egypt, and the East Indies. The fruit is a cylindrical pod, the pulp of which is a gentle laxative medicine.