Bluevine is often referred to as Cynanchum laeve; its scientific name has changed occasionally through the years. Other common names for this species are Honeyvine and Sandvine. A few members of the Milkweed family in Illinois are twining vines, rather than erect herbaceous plants. Most of these occur in southern Illinois in swampy habitats; they are currently classified as Matelea spp. (Climbing Milkweeds), although they were assigned to the Gonolobus genus in the past. The flowers of the Climbing Milkweeds have larger flowers with spreading corolla lobes; they are variously colored. The flowers of Bluevine are smaller with more erect corolla lobes. An introduced species, Vincetoxicum nigrum (Black Swallow-Wort), occurs occasionally in Illinois. It was formerly known as Cynanchum nigrum. Black Swallow-Wort has leaves that are rounded at the base and its flowers are brownish purple. All of these vines produce follicles (seedpods) that resemble those of other members in the Milkweed family.