Monographs Details: Exogonium arenarium (Steud.) Choisy
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - Elegant when in bloom, this slender, herbaceous vine, woody near the base, is at other times inconspicuous, because its leaves are small and not readily seen. It inhabits thickets of the nothern West Indies, climbing on bushes, mostly near the coasts, and ranges from Santo Domingo, through Porto Rico and the Virgin Islands, eastward to St. Martin and Anguilla of the northern Leeward Islands. In Porto Rico it is frequent in the dry, southwestern districts at lower and middle elevations, and has been near Rincon, on the western coast and at Bahia Puerco on the eastern; it grows also on the Porto Rican islands Vieques and Culebra. Its flowers are remarkably various in color, on different vines crimson, rose, lilac, purplish, or even White. The specific name arenarium (of the sand), refers to the growth of the plant in sandy soil, which it sometimes inhabits, but it also occurs in rocky situations. No attempt to bring the vine into gardens as an ornamental plant has been brought to our attention. The genus Exogonium, first described by the Swiss botanist Choisy in 1833, comprises some twenty-five species, all natives of tropical and subtropical America; besides the one here illustrated and described, two others are wild in Porto Rico, one of them growing near the northern and western coasts, the other in mountain forests. The derivation of the generic name is from the Greek, referring to the projection of the stamens and styles beyond the corolla. Some authors have included these plants in the genus Ipomoea, the Morning-glories, but the Exogoniums have a salverform corolla and projecting stamens, while in the Ipomoeas the corolla is funnelform and the stamens do not project from it. Exogonium arenarium is a smooth, twining or trailing vine, sometimes attaining a length of 4 meters or more, often considerably branched. Its leaves are only about 2 centimeters long, or smaller, thin and various in form, being nearly round in outline and often notched, or two-lobed, or four-lobed, the lobes narrow, or broad and usually blunt or rounded; The leaf-stalks are very slender. The flowers appear from 2 to 4 together, or solitatry in the leaf-axils, or short on stout stalks; the calyx is composed of five, blunt sepals about 6 millimeters long; the corolla is from 3 to 4 centimeters long, with a slender tube and a widely spreading slightly lobed limb nearly as broad as the length of the tube; the 5 stamens with the style, protrude about a centimeter, and the anthers are yellow, the stigma nearly globular. The fruit is a pointed capsule about 1 centimeter, containing several seeds which are covered with long, wool-like hairs. Our illustrations was first published in "Addisonia", plate 402, in 1927.

Discussion:Cambustera de arena Sand Exogonium Morning-glory Family Exogonium arenarium Choisy, Convolvulaceae Rariores 129. 1838.