HELLEBORUS, HELLEBORUS, in botany, a genus of the polyandria polygynia class. It has no calix; the petals are five or more; the nectarium is tubular and bilabiated; and the capsule contains many seeds. There are five species, two of them natives of Britain, viz. the fœtidus, or great bastard black hellebore; and the viridis, or wild black hellebore. The hellebore, when taken in large quantities, is poisonous; but the root, in small doses, is supposed to attenuate the humours, and to promote urinary and uterine discharges.