or perennial herbs. Stem 4-angled or sometimes inflated and almost leafless.
Leaves opposite, rarely whorled or alternate, sessile, linear to ovate.
Inflorescence axillary or terminal, many-flowered, bracteate heads or rarely
solitary. Calyx tube campanulate, urn-shaped, or semiglobose, sepals 4-8, with
or without appendages. Petals 0-8, corrugated in bud. Stamens 4-23. Ovary 2 to
5-celled, septum complete and therefore, continuous with the style, styles very
short to longer than the ovary, stigmas capitate. Fruit a capsule, opening with
a lid, later irregularly below. Seeds numerous.