TIARELLA, in botany: A genus of plants belonging to the class of decandria, and order of digynia; and in the natural system ranging under the 13th order, Succulenta. The calyx is quinquipartite; the corolla pentapetalous, and inserted into the calyx; the petals are entire; the capsule is unilocular and bivalve, the one valve being less than the other. There are two species, the cordifolia and trifoliata.