Erect, annual herb; 15-30 cm in height, simple or branched from the base, angles more or less scabrid; leaves subsessile, linear-oblong, narrowed at both ends, acute, more or less coriaceous, glabrous or scabrid, usually with recurved margins; stipules with many, long, bristles; flowers many in globose, compact, axillary or terminal heads; bracteoles filiform, hyaline, as long as or exceeding the calyx; calyx tube pubescent above, glabrous at base, teeth linear-subulate, pubescent; corolla white, tubular, very slender, glabrous within, lobes 4, linear, spreading, tips acute; stamens 4, epipetalous on the throat of corolla, filaments short, anthers oblong or linear; ovary 2-celled, stigma 2 lobed, subglobose, style filiform with 2-short arms; capsules oblong, narrowed at the base, membranous, glabrous below, crowned with erect calyx teeth; capsule dehising septicidally, both mericarps dehiscing ventrally; seeds 2, linear-oblong, highly polished, black or dark brown.