Perennial or rarely facultatively annual, prostrate or rarely suberect. Peduncle axillary, nude or with 1-several reduced bracts. Heads either bisexual with any proportion of pistillate and staminate florets or unisexual or both. Corolla of pistillate florets present, evident, tubular, conical to cylindric, sts compressed, persistent or deciduous, ca. as wide as ovary at anthesis, jointed with ovary, inflated with a hollow space between the outer surface and an inner layer closely surrounding the style. Disk florets seed-sterile, functionally staminate; ovary reduced but evident and demarcated from corolla; style apex an undivided, circular, slightly concave disc. Achene thick, not flat, convex on the dorsal surface at least, not winged but with an obvious or obscure margin, lacking blunt columnar uniseriate hairs on the dorsal and ventral surfaces, rarely with tapering uniseriate hairs on the margins. Chromosome number, x=13 (n = 26, 52 and ca. 78, 104, 130 and 156).