(Arabia). Cruciferre. ROCK-CBESB. Small perennial or annual herbs, with white or purple fls., grown mostly in rockwork. Fls. mostly in terminal spikes or racemes, small, but often many, or appearing for a considerable period of time : siliques long, linear, flat : stigma 2-lobed. In temperate regions, several na tive to this country. Usually prop. by division; also by seeds and cuttings. Hardy, requiring plenty of sun, and thriving even in poor soil. The following four species are perennials: