Description:

• Submerged herbaceous annuals or perennials, monoecious or dioecious, in fresh or brackish water
• Roots simple, adventitious, devoid of root caps
• Branches upright, repeatedly forked, brittle, smooth or prickly
• Leaves sessile, in pseudo-whorls of 3 or more, with an open, folded basal sheath and a linear, 1-veined, dentate lamina, with 2 axillary scales
• Flowers unisexual, small, solitary or sometimes aggregated above, water-pollinated
• Male flower a single stamen enveloped in bud by a closed spathe, with a thin inner membrane, bilobed at apex, closely adhering to the 1- or 2- or 4-thecous anther; pollen globose or ellipsoid, without exine, contents granular
• Female flower a single ovoid carpel surrounded by a spathe, or naked; ovule solitary, basal, erect, anatropous; style filiform, with 2(3) filiform stigmatic branches
• Fruit a small, narrowly ovoid nut; epicarp reticulated
• Seeds: embryo straight, with a large hypocotyl and radicle; endosperm 0
• x = 6 (7, 8, 17, 23) (high polyploidy, B-chromosomes)

Nomenclature:

• Najas L.
  • Linnaeus: 1015 (1753)
  • Bennett: 51 (1897)
  • Obermeyer: 82 (1966)
  • Triest: 19, 28, 44, 69 (1987)

Distribution & Notes:

• Global: Species ± 40
• Southern Africa: Species 4, 2 widespread, in fresh or brackish water in inland or coastal lakes
  • Najas graminea Delile has been collected twice, once in Gauteng and once in Mpumalanga; it is common in the rest of Africa
  • Najas setacea Rendle has been collected in Ndumu Game Reserve, KwaZulu-Natal; this is a new record for the continent of Africa