Acanthaceae
Creators: name: Manzitto-Tripp, Erin A.
name: Darbyshire, Iain
name: Daniel, Lucinda A. McDade Thomas F.
name: Kiel, Carrie A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Lamiales
Acanthaceae

description: 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
description: Published as part of Manzitto-Tripp, Erin A., Darbyshire, Iain, Daniel, Lucinda A. McDade Thomas F. & Kiel, Carrie A., 2022, Revised classification of Acanthaceae and worldwide dichotomous keys, pp. 103-153 in TAXON 71 (1) on pages 121-122, DOI: 10.1002/tax.12600, http://zenodo.org/record/14047424