Description:

• Floating aquatic herbs
• Adventitious roots developing from leaf scars of submerged leaves containing chlorophyll, pinnatisect into many filiform segments
• Leaves dimorphic; floating leaves alternate, forming rosettes, only present at upper nodes, with long spongy petiole ± inflated about middle, lamina deltoid to rhombic, upper margins toothed; submerged leaves opposite, sessile, linear, entire, falling off early; stipules small, scarious, divided to base and thus apparently more than 2 per leaf, linear, elongate, acuminate, deciduous
• Flowers bisexual, regular, solitary, axillary
• Calyx 4-lobed; tube oblong, slightly produced above ovary; lobes accrescent, often spinescent, hirsute at first, glabrescent
• Petals 4, free, subsessile, obovate, white
• Stamens 4, as long as calyx lobes; anthers oblong, 2-thecous
• Ovary half-inferior, 2-locular, with a single, pendulous, linear ovule in each locule; style thick, terete, as long as stamens; stigma globose
• Fruit a 1-seeded, top-shaped, bony or coriaceous drupe, horned with 2-4 persistent calyx lobes
• Seed solitary, filling fruit; testa woody; cotyledons very unequal, 1 almost vestigial
• x = 6 or 12 (polyploidy)

Nomenclature:

• Trapaceae
  • Linnaeus: 120 (1753)
  • Roessler 96 (1966)
  • Brenan: 346 (1978)
  • Verdcourt: 447 (1986)
  • Verdcourt: 11 (1998)

Distribution & Notes:

• Global: Genus 1, Eurasia and Africa; 1 polymorphic species or ± 15, depending on species interpretation
• Southern Africa: Genus 1, species 1 with 2 varieties

References:

• BRENAN, J.P.M. 1978. Trapa L. Flora zambesiaca 4
• LINNAEUS, C. 1753. Species plantarum. Laurentius Salvius, Stockholm
• ROESSLER, H. 1966. Trapaceae. Prodromus einer Flora von Südwestafrika 96
• VERDCOURT, B. 1986. Notes on Trapa for the 'Flora of southern Africa.' Kew Bulletin 41
• VERDCOURT, B. 1998. FSA contributions 10: Trapaceae. Bothalia 28

Resources:

• Trapaceae genus: Trapa