ALSTONIA, in botany; a genus of the monogynia order, belonging to the hexandria class of plants. The characters are: The calyx is a perianthium beneath, imbricated: The corolla is monopetalous, and shorter than the calyx; the border expanding, eight or ten parted, with alternate divisions: The stamens consist of numerous short filaments, the exterior ones longer; the anthers are orbicular and furrowed: The pistillum has a small ovate germen above; a simple style the length of the corolla, filiform and erect; the stigma inverse egg-headed. There is but one species, the theaformis, a native of America.