Eryngium. Eryngium aquaticum L. Button Snakeroot. Corn Snakeroot. Rattlesnake's Master.—The button snakeroot or water eryngo is an indigenous umbelliferous plant which grows in low wet places, from New Jersey as far south as Florida and Texas. The root, which is the medicinal portion, has a bitter, pungent aromatic taste, provoking, when chewed, a flow of saliva. It is said to be diaphoretic, expectorant, in large doses emetic, and the plant has been used as a substitute for senega.