ÆTHUSA, in botany, a genus of the pentandria digynia class. The volucrum is dimidiated, triphyllous, and pendulous. There is but one species, viz. the æthusa synapium, fools-parley, or lesser hemlock, (a native of Britain,) which grows in corn-fields and gardens. This plant, from its resemblance to common parley, hath sometimes been mistaken for it; and when eaten, it occasions sickness. If the curled-leaved parley only was cultivated in our gardens, no such mistakes would happen in future. Cows, horses, sheep, goats, and swine, eat it. It is noxious to geese.