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 genera of Acantheae
1 Corolla regularly 5-lobed or bilabiate, not comprising a single lip.... 2
1 Corolla lobes comprising a single lip, entire or 3- or 5-lobed, held either ventrally or dorsally, or if (rarely) not markedly 1-lipped [3] then at least with the sinus between the 2 uppermost (outermost) lobes clearly at a wider angle than that of the other sinuses ........ 8
2 Plants of tropical Africa and Madagascar ........ Stenandriopsis [4]
2 Plants of the Americas................................................................. 3
3 Corolla zygomorphic, the lobes dissimilar in form ..................... 4
3 Corolla usually subactinomorphic, the lobes more or less similar in form (or nearly zygomorphic with lobes of upper lip dissimilar from those of lower lip in some Stenandrium) ............................ 6
4 Calyx deeply 3-partite............................................. Cyphacanthus
4 Calyx 5-partite ............................................................................. 5
5 Leaves opposite (rarely subopposite), not quaternate; bracts entire or dentate, green or often brightly colored; corollas rarely with linear nectar guides, mostly 25–85 mm long; at least distal portion of filaments of stamens usually exserted from corolla tube; pollen with colpi not expanded or bifurcating (usually narrowed) toward poles, interapertural exine usually heterogeneously sculptured; plants typically of wet habitats; widespread in NW.................. Aphelandra [5]
5 Leaves opposite (rarely subopposite) or quaternate; bracts entire and usually green; corolla often with colored linear nectar guides, 6.5–24 mm long (or if longer [to 40 mm], then plants with quaternate leaves); filaments of stamens often entirely included in corolla tube; pollen with colpi sometimes expanded or bifurcating toward poles, interapertural exine homogeneously sculptured; plants of dry habitats; Mexico .................................................. Holographis
6 Pollen 3-colpate with each colpus longitudinally bisected by an operculum (elongate band of exine), opercula either isolated within the colpi (operculate) or connected at each end to the interapertural exine (pontoperculate); Jamaica ................................ Salpixantha [6]
6 Pollen 3-colpate with colpi not bisected by elongate bands of exine or pollen pantoforate (i.e., sometimes in Stenandrium dulce) or pollen pantoaperturate (rugate) with rugae arranged ± tangentially or irregularly over surface or pollen 3-colpate and with prominent margines and mesocolpial ridges (appearing 9-colpate); widespread, but not in Jamaica ............................................................ 7
7 Plants usually small, up to 25(–70) cm; leaves often borne at or near ground level (plants acaulescent to subcaulescent); bracts usually green; widespread .............................................. Stenandrium
7 Plants usually shrubby, up to 1.5 m tall; leaves disposed along conspicuous stems; bracts whitish, pinkish, or reddish-brown; Central America and South America............................... Neriacanthus [6]
8 Corolla tube twisted through 180°, the single corolla lip held dorsally, entire or 3-lobed; Tanzania ............................. Streptosiphon
8 Corolla tube not twisted, corolla lip held ventrally, 3- or 5-lobed or sometimes only undulate ............................................................. 9
9 Stamens included in corolla tube, anthers subsessile, not inserted on a thickened flange................................................................. 10
9 Stamens exserted from corolla tube, with flattened bone-like filaments, inserted on a thickened flange........................................ 11
10 Calyx 4-lobed, anterior lobe bifid; bracts not imbricate, smaller than bracteoles; bracteoles conspicuous, elliptic or obovate, diverging widely from inflorescence axis; corolla tube not narrowly cylindrical, limb obscurely 5-lobed or erose .......................... Crossandrella
10 Calyx 5-lobed; bracts usually imbricate, larger than and enclosing bracteoles; bracteoles linear to lanceolate, not diverging widely from inflorescence axis; corolla tube narrowly cylindrical, limb 5-lobed........................................................................ Crossandra
11 Calyx 5-lobed; seeds sculpted with pectinate scales or concentric rings; bracts, bracteoles and calyx lobes glumaceous ... Sclerochiton
11 Calyx 4-lobed; seeds either covered in hygroscopic trichomes, puberulous or glabrous, or seeds tuberculate, without scales or concentric rings; bracts, bracteoles and calyces only rarely glumaceous......................................................................... 12
12 Anterior pair of staminal filaments flattened and either with an obtuse or acute tooth-like appendage or truncate to rounded towards apex ventrally ............................................................................ 13
12 Anterior staminal filaments lacking appendages, if flattened then gradually narrowed towards apex .............................................. 14
13 Leaves opposite; flowers solitary or paired in leaf axils, each subtended by 2 pairs of bracteoles, outer pair entire, inner pair trifid; ovary without apical tufts of glandular trichomes; seeds tuberculate; India ............................................................ Cynarospermum
13 Leaves in pseudowhorls of (3) 4; inflorescences variable but not with single or paired flowers in leaf axils; bracteoles entire or toothed, not trifid; ovary with 2 apical tufts of glandular trichomes; seeds with branched hygroscopic trichomes; widespread.............. ....................................................................................... Blepharis
14 Seeds glabrous or sericeous-puberulous; stigma bilobed; bracts terminating in a single spine; plants often robust, ± tall perennial herbs, shrubs or small trees; widespread ........................ Acanthus
14 Seeds covered in long hygroscopic trichomes; stigma 1-lobed; bracts terminating in 3 or 5 simple or compound spines; plants often compact shrublets or acaulescent perennial herbs, if taller then slender; SW Africa .................................................... Acanthopsis
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 page 122, DOI: 10.1002/tax.12600, http://zenodo.org/record/14047424