Flowers of the convolvulaceae (morning glory, or bindweed) family are radially symmetric, and quite distinctive; they have five sepals around the base of a tubular, funnel-shaped corolla which opens to five fused petals, often pentagonal or nearly circular when viewed from the top, though some species have projecting petal tips. Plants are variable in form; herbs, shrubs, trees or vines, the latter most common. Five stamens rise from the center of the tube, generally not extending past the petals. Leaves (where present) are simple. There are 18 genera and around 200 species in the US; the largest genera include calystegia, convolvulus, cuscuta, and ipomoea.