ERYSIMUM, in botany, a genus of the tetradymania filiquosa class. The pod is four-sided, divided into two cells. There are six species, four of which are natives of Britain, viz. the officinale, or hedge-mustard; the cheiranthoides, or treacle worm-feed; the barbara, rocket, or winter-cresses; and the alliaria, Jack-by-the-hedge, or lawce-alone. The leaves of the hedge-mustard are said to promote expectoration, and to excite urine and other excretions.