Table 1 in Revised classification of Acanthaceae and worldwide dichotomous keys

Table 1. Key morphological characters for the major lineages of Acanthaceae. Table includes some exceptions to general trends within a given lineage but is not comprehensive in terms of all exceptions that exist.
CharacterNelsonioideaeAvicennioideaeThunbergioideaeAcantheaePhysacantheaeAndrographideaeBarlerieaeNeuracantheaeWhitfieldieaeRuellieaeJusticieaeCharacterCystolithsAbsentAbsentAbsentAbsentAbsentPresentPresentPresentPresentPresentPresentCystolithsCorolla aestivationDescendingcochlearLeft-contort, slightly imbricate, or valvateLeft-contort; rarely ascendingcochlearAscendingcochlear or “open”Left-contortAscendingcochlearQuincuncialInduplicateLeft-contortLeft-contortAscending-cochlearCorolla aestivationNo. of fertile stamens2 or 4444422 or 442 (Lankesteria) or 42 or 42 or 4No. of fertile stamensNo. of anther thecae per fertile stamen2221122, or mixed 2×2-thecous and 2×1-thecousMixed 2×2-thecous and 2×1-thecous221 or 2; if 4 stamens then 2-thecous or mixed 2×2-thecous, 2×1-thecousNo. of anther thecae per fertile stamenPollen characteristics3-colpate to 3-colporate, pseudocolpi absent3-colporate, pseudocolpi absentSpiraperturate, 3–6-colpate, or 7–9-lobate and -colpate, pseudocolpi absentUsually 3-colpate, sometimes with numerous short colpus-like apertures dividing grains into polygonal regions, rarely with pseudocolpi3-colporate, 9-pseudocolpate3-colporate, 3-pororate, ectoapertural membrane and/or thickened margin often with spines, pseudocolpi absentMostly 3-colporate or 3-porate, interapertural exine often coarsely reticulate, pseudocolpi absent ͡3-colporate, interapertural exine finely perforate, pseudocolpi absentUsually lenticular, 2-pororate with ectoaperture usually very large, sometimes 3-pororate or spherical and pantoforate, pseudocolpi absentDiverse; germinal apertures 2 to many, porate to colporate or pantoforate; tectum often raised flanking apertures, pseudocolpi often present and usually more than 2 between germinal aperturesDiverse, germinal apertures 2–6, (porate to) pororate to colporate, pseudocolpi often present but rarely (if ever) more than 2 between germinal aperturesPollen characteristicsFruit characteristicsMostly small capsules varying from thin- to thickwalled, sometimes rostrateLeathery to fleshy capsule that is non-explosive, and tardily dehiscentLarge woody rostrate capsule; OR globose or ellipsoid drupeFusiform or shortly rostrate capsuleLinear capsuleLinear and 4-angular or compressed elliptic, oblanceolate or narrowly oblong capsuleFusiform or rostrate capsule, rarely stipitateFusiform or rostrate capsuleStipitate or fusiform capsuleStipitate, linear or fusiform capsuleStipitate, sometimes also shortly rostrate capsuleFruit characteristicsHooked retinaculaAbsentAbsentAbsentPresentPresentPresentPresentPresentPresentPresentPresentHooked retinaculaNo. of ovules*8 to many41, 2 or 446–104 to many42 or 42 or 42–322 or 4No. of ovules*No. of seeds*8–30 (–68)11, 2 or 42–4(4–) 6–104 to many2–42–42–42–282–4No. of seeds*Seed sculpture / trichomesVariably smooth, pitted, with minute protrusions and with or without hygroscopic trichomes (these simple or branched)SmoothSmooth or sculptured, with a prominent scar or hole on one side (in drupaceous genera, a woody stone)Dense hygroscopic trichomes, dense scales or tuberculate, glandular puberulous, smooth or glabrous, or otherwise variableWith pale straight or flexuose papillae-like trichomesWith or without dense hygroscopic trichomes or non-hygroscopic trichomes, smooth or sculpturedDense hygroscopic trichomes or fine?non-hygroscopic trichomes, rarely glabrous and smoothDense hygroscopic trichomesRaised concentric rings at least towards the rim; glabrous or (Lankesteria) with hygroscopic trichomesDense hygroscopic trichomes or these restricted to the rim, rarely absentSmooth or often sculptured (tubercles, spines, verrucae, etc.), and/or with hygroscopic or non-hygroscopic trichomesSeed sculpture / trichomesOther diagnostic or informative charactersFlowers often alternate to spirally arranged on inflorescence, although can be oppositeMangrove shrubs or trees with pneumatophores, and plants cryptoviviparousOften twiners; flowers subtended by paired clasping bracteolesLeaves often variegated; long-cylindric or inflated calyx with short lobesCystoliths can occur in adjoining cellsCalyx bilabiate (anterior lip 2-notched, posterior lip 3-notched)Inflorescence units often subtended by conspicuous paired clasping bracteolesFilament curtain usually present, and thecae sometimes with basal appendagesAnther thecae sometimes offset to superposed and/or oblique, and one or both thecae sometimes with basal appendagesOther diagnostic or informative characters