Description:

• Submerged, fern-like, annual or rarely perennial herbs found on rocks in fast-flowing freshwater, dioecious or rarely monoecious; rhizome discoid or tuberous, forming a compact circle of roots, firmly attached to rocks
• Leaves basal, 2- or 3-pinnatifid, petiolate, dilated and ligulate at base, petiole and rachis densely covered with warty to tongue-shaped protuberances; pinnae dissected into multifid, variously-shaped outgrowths ('gill-tufts')
• Inflorescence emergent, densely spicate (resembling fruiting spikes of Plantago major); scape verrucose or rarely smooth
• Flowers unisexual, small, sessile, solitary in axils of spirally arranged, closely imbricate bracts; calyx and corolla 0
• Male flowers consisting of one sessile or subsessile stamen with 2 oblong thecae; pollen in tetrads, copious
• Female flowers: ovary superior, of 2 fused carpels, 1-locular, many-ovuled, with 2 parietal placentas; styles 2, exserted from the bracts, persistent
• Fruit a 2-valved capsule, enclosed in persistent bract
• Seeds small, light, many; endosperm 0

Classification Notes:

• In habit the family closely resembles Podostemaceae, and the two were formerly often considered to be affiliated. Recently Hydrostachyaceae has been placed in or near SCROPHULARIALES, LAMIALES or PLANTAGINALES. Chemical data support affiliations with BRUNIALES

Nomenclature:

• Hydrostachyaceae
  • Podlech: 1 (1966)
  • Obermeyer: 211 (1970)
  • Cusset: 75 (1973)
  • Cook: 105 (1990)
  • Scogin 471 (1992)
  • Stannard 10 (1997)

Distribution & Notes:

• Global: Genus 1, species 22, Africa south of the equator and Madagascar
• Southern Africa: Genus 1, species 1

References:

• COOK, C.D.K. 1990. Aquatic plant book. SPB Academic Publishing, The Hague
• CUSSET, C. 1973. Révision des Hydrostachyaceae. Adansonia, sér. 2, 13 (1)
• OBERMEYER, A.A 1970. Hydrostachyaceae. Flora of southern Africa 13
• PODLECH, D. 1966. Podostemaceae. Prodromus einer Flora von Südwestafrika 61
• SCOGIN, R. 1992. Phytochemical profile of Hydrostachys insignis (Hydrostachyaceae). Aliso 13(3)
• STANNARD, B.L. 1997. Hydrostachyaceae. Flora zambesiaca 9,2

Resources:

• Hydrostachyaceae genus: Hydrostachys