NERIUM, in botany: A genus of the monogynia order, belonging to the pentandria class of plants; and in the natural method ranking under the 30th order, Centortae. There are two erect follicles; the seeds plumy; the tube of the corolla terminated by a lacerated crown. There are five species, all of them natives of the warmer climates: the most remarkable of which are, 1. The oleander, South-Sea rose: this is a beautiful shrub, cultivated in gardens on account of its flowers, which are of a fine purple, and in clusters, but of an indifferent smell: the whole plant is poisonous, and especially the bark of the roots. 2. The antidyfthericum, a native of Ceylon: the bark of which is an article of materia medica, under the name of Coniffi. 3. The tinctorium, a new species with beautiful blue flowers lately discovered by Dr. Rosburgh at Madras. A decoction of the leaves, with an addition of lime-water, makes an indigo of fine quality.