Description:

• Annual or perennial herbs, simple or branched, sometimes tufted; stems quadrangular, glabrous to glandular-villous or hirsute
• Leaves mostly opposite, sometimes alternate near inflorescence, petiolate, lanceolate to ovate, entire or dentate to pinnatifid, apex acute
• Flowers 1-several in lax terminal racemes, alternate, resupinate by twisting of pedicels
• Bracts leafy or bractiform, ovate to linear
• Calyx 5-lobed; segments lanceolate or narrowly elliptical, somewhat unequal, entire or irregularly incised, imbricate at base in bud
• Corolla expanded, bilabiate, unequally 5-lobed, tube very short, split to base on anterior side (morphologically posterior side); limb spreading; upper lip (actually lower one) 3-lobed, central one largest, broadly ovate, lateral ones ovate or broadly so, gamopetalous portion at base of lateral lobes with 2 shallow sacs lined with oil-secreting hairs; lower lip (actually upper one) split centrally to base, of 2 broad lobes, exterior in bud
• Stamens 4, all perfect, didynamous; filaments short, basally declinate, not twisted round each other, glabrous, or glandular-puberulent; anthers shortly oblong, unithecate by confluence; staminodes 0
• Ovary bilocular, ovate or widely ovate, obtuse or emarginate; ovules many; style involute, subulate, persistent; stigma capitate or minutely bifid
• Fruit an ovate or pyriform, emarginate, septicidally bivalved capsule; valves entire, emarginate or bifid
• Seeds many, small, ovoid or oblong to elliptic, wingless, a little depressed at both ends, dark brown with shallow longitudinal grooves, punctate-rugose or papillate
• x = 7, 12, 25 (1 report each, aneuploids, polyploidy)

Nomenclature:

• Alonsoa Ruiz & Pav.
  • Ruiz & Pavón: 150 (1798)
  • Wettstein: 53 (1891/1893)
  • Hiern: 138 (1904)
  • Hilliard & Burtt: 338 (1984)
  • Roux: 7 (1986)
  • Steiner: 1152 (1989)
  • Steiner: 63 (1996)
• Schistanthe Kunze
  • Kunze: 109 (1842)
  • Bentham: 249 (1846)
  • Wettstein: 53 (1891/1893)

Distribution & Notes:

• Global: Species 16, mainly South American, ranging from Mexico to Chile, centred in Peru
• Southern Africa: Species 2: Alonsoa peduncularis (Kunze) Wettst., Western and Eastern Cape (restricted to Rooiberg, Touwsberg and near Uitenhage), and A. unilabiata (L.f.) Steud. from Western Cape, but probably extinct near Cape Town
  • South African species of Alonsoa differ from South American ones in having 2 shallow, trichome-lined sacs on corolla
  • Oil-collecting bees act as pollinators