| + | Flowers small, the calyx with acute teeth; corolla bell-shaped, with 5 appendages inside; stamens 5, inserted deep in the corolla, the filaments very short; style 0: seeds silky.—Tough perennial herbs, with milky juice, chiefly of north temperate zone, with oblong or ovate, opposite Lvs., milkweed-like fls. in small cymes, and slender follicles or pods. About 25 species, 10 native to N. Amer. |