A large family, widely distributed, most abundant in warm regions; ours are perennial herbs, usually with milky juice and tough fibrous inner bark; leaves generally large, toothless, without stipules; flowers peculiar in shape, in roundish clusters; calyx with a short tube or none and five lobes; corolla five-lobed; stamens five, on the base of the corolla, with short, stout filaments, anthers more or less united around the disk-like stigma, which covers and unites the two short styles of the superior ovary. The two parts of the ovary develop into two conspicuous pods, opening at the side, containing numerous flattish seeds, arranged along a thick, central axis, usually each with a tuft of silky down to waft it about.

There are many kinds of Asclepias, with oddly-shaped flowers, interesting and decorative in form; calyx rather small, the pointed sepals turned back; corolla with its petals turned entirely back, so as to cover the sepals and expose the peculiar-looking central arrangements of the flower, called the "crown." In the middle is the large, flat, shield-shaped, five-lobed or five-angled stigma, surrounded by the anthers, which are more or less united to each other and to the stigma, encircled by five, odd, little honey-bearing hoods, the same color as the petals, each with a horn, either enclosed within it or projecting from it, the whole collection of stigma, anthers, and hoods, forming the "crown." The pods are thick and pointed. Named for ∆sculapius, as some of these plants are medicinal. Indians used to make twine from the fibrous bark of some kinds.