SWERTIA, MARSH GENTIAN, in botany: A genus of plants belonging to the class of pentandria, and to the order of digynia; and in the natural system ranging under the 20th order, rotacea. The corolla is wheel-shaped. There are nectariferous pores at the bases of the segments of the corolla. The capsule is unilocular and bivalve. There are six species; the perennis, disformis, rotata, carinthiaca, corniculata, dichotoma. The perennis is a native of England. It is distinguished by radical oval leaves. It flowers in August.