S. nodosa: stems erect, 2-3 feet high, glabrous, sharply quadrangular, the short stock emitting a number of green knots or tubers; leaves broadly ovate or heart-shaped, acute serrated; panicle loosely pyramidal or oblong, the corolla lurid greenish-purple. - Moist hedges and thickets. Fl. June, July.
S. aquatica: stem 2-5 feet high, the angles projected into narrow wings; leaves cordate-oblong, obtuse; panicle long, narrow, the flowers dull purple. - Ditches and sides of streams. Fl. July, August. [See also p. 60.]