* Leaves opposite, densely crowded.
S. oppositifolia: stems creeping; leaves small, opposite, obovate, overlapping, fringed; flowers large, purple, solitary, on short erect branches, but so numerous as to cover the stems. - Alpine rocks. Fl. April.
** Leaves alternate, the upper ones distant.
S. tridactylites: annual; stem short, erect, usually red; leaves small, entire or three-lobed; flowers small, white. - Walls and dry barren places. Fl. April, May.