Acanthaceae Acanthoideae Thunbergioideae

Manzitto-Tripp, Erin A., Darbyshire, Iain, Daniel, Lucinda A. McDade Thomas F. & Kiel, Carrie A., 2022, Revised classification of Acanthaceae and worldwide dichotomous keys, TAXON 71 (1), pp. 103-153 : 121-122

Key to the subfamilies of Acanthaceae

Fruit a capsule with seeds held on hooked retinacula (retinacula malformed or not discernible in Aphanosperma and Chalarothyrsus and seeds permanently retained in capsule valves); cystoliths present or if absent then anthers monothecous ....... Acanthoideae

Key to the genera of Nelsonioideae [2]

Peduncles (if present) bearing alternate to spirally arranged, clasping scale-like sterile bracts; bracts sclerophyllous to coriaceous; leaves alternate and diffuse along stems or in rosettes or whorls either basally or terminating branches; stigma scarcely divided, touch-sensitive, folded over and enclosing anthers in undisturbed flowers, becoming erect when touched............................ Elytraria

Fruit a capsule or a drupe; if a capsule, then without hooked retinacula; cystoliths absent; anthers bithecous ................................ 2

Mangrove trees or shrubs with pneumatophores; fruit a leathery 1-seeded capsule ................................................... Avicennioideae

Peduncles (if present) without clasping scale-like bracts; bracts membranous or foliaceous; leaves opposite (sometimes subopposite or alternate in Nelsonia and Staurogyne ), at least some pairs dispersed along the stems; stigma usually conspicuously lobed, neither folded over nor enclosing anthers, not touch-sensitive .................... 2

Herbs, shrubs or lianas, not mangrove trees or shrubs, pneumatophores absent; fruit a capsule with 2 or more seeds, or a 1–2-seeded drupe...3

Herbs or shrubs, not twining; paired bracteoles present or absent but never large and conspicuous; flowers usually alternate or spirally arranged in few- to many-flowered inflorescences; calyx deeply 4- or 5-lobed;fruit a many-seeded (usually>10seeds) capsule ..................................................................................... Nelsonioideae

Bracteoles absent; inflorescence of dense ± cylindrical spikes with imbricate bracts; calyx 4-lobed, the anterior lobe with bifid apex (rarely more deeply divided into 5 lobes); stamens 2, staminodes absent............................................................................... Nelsonia

Climbing herbs or lianas, less frequently free-standing shrubs or perennial herbs; flowers subtended by conspicuous clasping or partially connate (at anthesis) paired bracteoles; flowers solitary or in fascicles or racemes of mostly opposite flowers, never spirally arranged; calyx a subentire or undulate rim or with irregular teeth, or shallowly 5-lobed; fruit either a 1–2-seeded drupe or a 2–4- seeded woody capsule....................................... Thunbergioideae

Bracteoles present; inflorescence variable but if spikes cylindrical then not so dense (except in Anisosepalum ); calyx 5-lobed; stamens 4, adaxial staminode often also present (rarely reduced to 2 stamens + 2–3 staminodes).......................................................... 3

Pairs of bracteoles inserted below receptacle, not adnate to it or to base of calyx tube (leaves not ternate and corollas usually less than 3 cm long).................................................................... Staurogyne

Pairs of bracteoles partially adnate to receptacle and sometimes also to base of calyx tube (or if bracteoles sometimes free in Anisosepalum lewallei , then leaves mostly ternate and corollas 3–4 cm long) ....... 4

Key to the tribes of Acanthoideae

Cystoliths absent; stamens 4, monothecous................................. 2

Cystoliths present; stamens 2 or 4, if 4 then at least 2 of these bithecous...................................................................................... 3

Calyx lobes subequal but similar to one another and not hidden by bracteoles; ovary asymmetric with style arising on one side, stigma 1-lobed, lobe apically subcapitate; Brazil................... Aymoreana

Calyx long-tubular, cylindrical to inflated; pollen colporate; capsule with more than 4 seeds; corolla aestivation left-contort..................... ............................................................................... Physacantheae [1]

Lateral 2 calyx lobes markedly shorter than other lobes and often hidden by the bracteoles; gynoecium not with the above combination of characters; Africa, Madagascar........................................ 5

Calyx not as above; pollen colpate; capsule with up to 4 seeds; corolla aestivation ascending-cochlear ............................ Acantheae

Plants delicate trailing herbs; petiole usually longer than leaf blade; anther thecae with a basal appendage, this often forked; corolla widened almost to the base into a campanulate throat, palate of lower lip not bullate, i.e., without raised bosses ...................... Saintpauliopsis

Calyx strongly bilabiate, with a 2-lobed or -toothed anterior lip and a 3-lobed or -toothed posterior lip; androecium usually of 2 bithecous stamens and 2 monothecous stamens (rarely 4 bithecous stamens); corolla with a funnel-shaped limb comprising equal anterior and lateral lobes and partially (or almost completely) fused dorsal pair of lobes, not strongly bilabiate........................ Neuracantheae

Plants erect or procumbent herbs or subshrubs; petiole usually shorter than leaf blade; anther thecae with basal appendages absent or short, apiculate, not forked; corolla with a cylindrical basal tube, and ± gradually widened throat, not appearing campanulate, palate of lower lip bullate, i.e., with raised bosses................ Anisosepalum

Above combination of characters lacking; if androecium of 2 bithecous stamens and 2 monothecous stamens then corolla strongly bilabiate ......................................................................................... 4

Corolla with left-contort aestivation in bud ................................. 5

Corolla with either quincuncial or ascending-cochlear aestivation in bud........................................................................................... 6

Key to the genera of Thunbergioideae

Fruit a fleshy drupe with 1 or 2 seeds.......................................... 2

Corolla tube with a filament curtain present (in all but 4 genera); seeds with trichomes either covering entire surfaces or along rim, often hygroscopic, seed surface without concentric ridges............ ........................................................................................ Ruellieae

Fruit a woody capsule with 2 or 4 seeds...................................... 3

Drupe 2-seeded, large (3–10 cm in diam.) ........... Anomacanthus

Drupe 1-seeded, not so large ....................................... Mendoncia

Stigma ± equally 2-lobed, each lobe subdivided into 2 unequal lobes; pollen 7–9-lobate and -colpate .............................. Meyenia

Corolla tube lacking a filament curtain; seeds sculptured with concentric ridges at least towards the rim, lacking trichomes, or if hygroscopic trichomes covering the seed surface ( Lankesteria only) then with the unique combination of: corolla salverform with a long narrowly cylindrical tube and a spreading 5-lobed limb, sometimes with the sinus between the anterior pair of lobes broader than the other sinuses ........................................................ Whitfieldieae

Corolla with quincuncial aestivation............................. Barlerieae

Corolla with ascending-cochlear aestivation................................ 7

Capsule 6–20-seeded or rarely 4-seeded; pollen with apertural margin or surface conspicuously thickened and often intricately ornamented with conical spines, pseudocolpi absent........................ ......................................................................... Andrographideae

Capsule 2- or 4-seeded; pollen variable but without conspicuously thickened and ornamented apertural margins or surfaces, pseudocolpi often present ......................................................... Justicieae

Stigma funnel-shaped, capitate, unequally 2-lobed or if equally lobed then not subdivided; pollen spiraperturate and unlobed .... 4

Anthers opening by apical pores; seed with a scar on the proximal face; indumentum stellate, bracteoles with a dense orange, red or mustard-yellow stellate indumentum covering the external surface ................................................................................... Pseudocalyx

Anthers opening by longitudinal slits; seed hollow on the proximal face; indumentum rarely stellate, bracteoles without a very dense orange, red or mustard-yellow indumentum externally.... Thunbergia