Description:

• Herbs, shrublets, shrubs, sometimes climbers or small trees, often with ± swollen nodes, sometimes spiny
• Leaves opposite, rarely radical (Elytraria), mostly entire, simple, lamina often with cystoliths (mineral concretions) showing up as streaks or protuberances in dried material; stipules 0
• Inflorescence based on dichasial and monochasial cymes; mostly bracteate, bracts often conspicuous, leaf-like or petaloid and subtending individual flowers
• Flowers bisexual, mostly irregular
• Calyx 4- or 5-partite (10-18-partite in Thunbergia), rarely 2-lipped, mostly shorter than corolla
• Corolla gamopetalous, 1- or 2-lipped, or (3, 4)5-lobed, sometimes resupinate; tube cylindric, funnel-shaped or campanulate; when 2-lipped upper lip usually entire, emarginate or 2-toothed, sometimes with a rugula (central channel) accommodating the style, and sometimes with lateral staminal channels accommodating the stamens (in Adhatoda); lower lip 3-lobed or 3-toothed
• Stamens arising on corolla, alternating with lobes, usually 4, sometimes didynamous, or 2, included or exserted; filaments normally linear; anthers 1- or 2-thecous, with thecae parallel to superposed, muticous or variously elaborated at base, sometimes ciliate; pollen prolate or, less often, sphaeroidal, 2- or 3- (col)porate; staminodes mostly 0, occasionally (1)2(3)
• Disc nectariferous, annular to deeply cupuliform
• Ovary superior, 2-carpellate, 2-locular, with (1)2(3 or more) axile, usually anatropous ovules in each locule; style terete or long-filiform, included or exserted; stigma simple, or equally, or unequally 2-lobed
• Fruit a 2-locular, loculicidally, often explosively, dehiscent capsule, ± club-shaped or ellipsoid; in a few genera placentas are elastic (i.e. remain attached to top of capsule and spring up from base)
• Seeds mostly borne on a retinaculum or jaculator (an elaboration of the funicle) except for a few genera of controversial inclusion (Elytraria, Nelsonia, Thunbergia), usually as many as ovules, usually ± lenticular, sometimes ± globose, smooth, rugose, tuberculate or muricate, sometimes covered with hygroscopic hairs or with hygroscopic hairs restricted to rim; endosperm 0 (except in Nelsonioideae); embryo large

Nomenclature:

• Acanthaceae
  • Burkill & Clarke: 1 (1899)
  • Burkill & Clarke: 193 (1900)
  • Clarke: 1 (1901)
  • Meyer: 1 (1968)
  • Balkwill & Immelman: 1 (1995)
  • Mabberley: 4 (1997)

Distribution & Notes:

• Global: Genera ± 350; species ± 4350, abundant in tropics and subtropics
• Southern Africa: Genera 42, species ± 350
• Notes: *Acanthus pubescens (Oliv.) Engl. is found as an occasional garden escape in the Northern Province

References:

• BALKWILL, K. & IMMELMAN, K.L. 1995. Acanthaceae. Subtribe Justiciinae. Flora of southern Africa 30,3,1
• BURKILL, I.H. & CLARKE, C.B. 1899. Acanthaceae. Flora of tropical Africa 5
• BURKILL, I.H. & CLARKE, C.B. 1900. Acanthaceae. Flora of tropical Africa 5
• CLARKE, C.B. 1901. Acanthaceae. Flora capensis 5,1
• MABBERLEY, D.J. 1997. The plant-book. Cambridge University Press, Cambridge
• MEYER, P.G. 1968. Acanthaceae. Prodromus einer Flora von Südwestafrika 130

Resources:

• Classification of Acanthaceae
• Key to Acanthaceae genera

• Acanthaceae genera: