Description:

• Shrubs, low growing or up to 1 m high and erect; branches much lignified; cortical bundles 0; epidermal bladder cell idioblasts small and much flattened; roots thickened
• Leaves decussate throughout and shortly connate at base, subcylindrical, deciduous; with distinct central water storing tissue
• Flowers in dichasia, up to 40 mm in diameter, white or bright pink on inside, suffused in different shades on outside; open during day, evening, or night
• Sepals 4; sepals, petals and stamens basally connate into a short tube
• Petals in several series, narrowly linear, white or pink, suffused in different shades of yellow, copper, pink or red on outside
• Stamens erect; pollen tricolpate, tectum punctate or punctate-foveolate, microspinulose or spinulose
• Nectary composed of 4 shell-shaped depressions
• Ovary semi-inferior, placentation axile; stigmas 4 or 5, subulate, 3(5 mm long
• Fruit a Mesembryanthemum type capsule, 4- or 5-locular, hygrochastic, usually opening and closing repeatedly, rarely opening only once and not closing again; expanding keels parallel; valve wings present; fruit breaking off easily and stalks becoming spiny
• Seeds D- or horseshoe-shaped, ± 1.5 mm long, brown or dark brown, with or without a crest; testa cells with central papillae, in distinct or indistinct concentric rows
• x = 9 (polyploidy)

• Flowering spring to early summer

• Distinguishing characters:
  • Stems woody
  • Leaves with flattened bladder cell idioblasts
  • Fruits upper and lower parts of equal proportions

Nomenclature:

• Aridaria N.E.Br.
  • Brown: 433 (1925)
  • Friedrich: 16 (1970)
  • Herre: 84 (1971)
  • Gerbaulet: 41 (1996)
  • Smith et al.: 30 (1998)
• Manettia Adans.
  • Adanson: 242 (1763) name illegitimate
• Nycteranthus Necker ex Rothmaler
  • Rothmaler: 413 (1941) name illegitimate
• Phyllobolus subgen. Aridaria (N.E.Br.) Bittrich
  • Bittrich: 74 (1986)
  • Hartmann: 47 (1993)

Distribution & Notes:

• Southern Africa: Species 4, southern and central Namibia and in karroid areas of the Western, Eastern and Northern Cape