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3. Acanthaceae
爵床科 jue chuang ke
Authors: Yunfei Deng, Jia-qi Hu, Thomas F. Daniel, John Wood & John R. I. Wood
Prostrate, erect, or rarely climbing herbs (annual or perennial), subshrubs, shrubs, or rarely small trees, usually with cystoliths (except in following Chinese genera: Acanthus, Blepharis, Nelsonia, Ophiorrhiziphyllon, Staurogyne, and Thunbergia), isophyllous (leaf pairs of equal size at each node) or anisophyllous (leaf pairs of unequal size at each node). Branches decussate, terete to angular in cross-section, nodes often swollen, sometimes spinose with spines derived from reduced leaves, bracts, and/or bracteoles. Stipules absent. Leaves opposite [rarely alternate or whorled]; leaf blade margin entire, sinuate, crenate, dentate, or rarely pinnatifid. Inflorescences terminal or axillary spikes, racemes, panicles, or dense clusters, rarely of solitary flowers; bracts 1 per flower or dichasial cluster, large and brightly colored or minute and green, sometimes becoming spinose; bracteoles present or rarely absent, usually 2 per flower. Flowers sessile or pedicellate, bisexual, zygomorphic to subactinomorphic. Calyx synsepalous (at least basally), usually 4- or 5-lobed, rarely (Thunbergia) reduced to an entire cupular ring or 10-20-lobed. Corolla sympetalous, sometimes resupinate 180º by twisting of corolla tube; tube cylindric or funnelform; limb subactinomorphic (i.e., subequally 5-lobed) or zygomorphic (either 2-lipped with upper lip subentire to 2-lobed and lower lip 3-lobed, or rarely 1-lipped with 3 lobes); lobes ascending or descending cochlear, quincuncial, contorted, or open in bud. Stamens epipetalous, included in or exserted from corolla tube, 2 or 4 and didynamous; filaments distinct, connate in pairs, or monadelphous basally via a sheath (Strobilanthes); anthers with 1 or 2 thecae; thecae parallel to perpendicular, equally inserted to superposed, spherical to linear, base muticous or spurred, usually longitudinally dehiscent; staminodes 0-3, consisting of minute projections or sterile filaments. Disk annular and nectar-producing at base of ovary. Ovary superior, 2-locular, placentation axile, with 2 to many ovules per locule; style filiform, simple; stigma funnel-shaped or 2-lobed (one lobe sometimes suppressed), one or both lobes sometimes recurved or recoiled. Fruit a loculicidal, stipitate or not, 2-valved, explosively dehiscent capsule [rarely drupaceous], 2- to many seeded, apex with or without a beak; septa remaining attached to or separating from inner wall of mature capsule. Seeds usually borne on hooklike retinacula (attached to septa of capsule), or retinacula lacking (Nelsonia, Ophiorrhiziphyllon, Staurogyne, Thunbergia), surface smooth or roughened, pubescent or lacking trichomes, sometimes with hygroscopic trichomes that expand when moistened.
About 220 genera and ca. 4,000 species: pantropical and subtropical, with a few species in temperate regions; 35 genera (one endemic) and 304 species (134 endemic, eight introduced) in China.
Pollen characters have traditionally been important in delimiting genera and higher taxa in the family; they are used sparingly in the key below. Avicennia Linnaeus, usually placed in either Verbenaceae (and treated as such in Fl. China 17: 49. 1994) or Avicenniaceae, is now included in Acanthaceae on the basis of molecular phylogenetic studies (e.g., A. E. Schwarzbach & L. A. McDade, Syst. Bot. 27: 84-98. 2002). The major economic importance of the family is horticultural. Species of Acanthus, Aphelandra R. Brown, Barleria, Crossandra Salisbury, Eranthemum, Fittonia Coemans, Justicia, Odontonema Nees, Pachystachys Nees, Ruellia, Sanchezia Ruiz & Pavon, Thunbergia, and numerous other genera are widely cultivated as ornamentals. Many species are cultivated in China but not treated in the present account. These include: Aphelandra squarrosa Nees, Barleria lupulina Lindley, Crossandra infundibuliformis (Linnaeus) Nees, Eranthemum pulchellum Andrews, Fittonia albivenis (Veitch) Brummitt, Justicia betonica Linnaeus, J. brandegeeana Wasshausen & L. B. Smith, J. carnea Lindley, Pachystachys lutea Nees, Ruellia elegans Poiret, R. simplex C. Wright, Sanchezia parvibracteata Sprague & Hutchinson, Thunbergia erecta (Bentham) T. Anderson, and T. laurifolia Lindley. Hu Chiachi & Tsui Hongpin. 2002. Acanthaceae. In: Hu Chiachi, ed., Fl. Reipubl. Popularis Sin. 70: 1-309.
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| 1 |
Vines; calyx cupular with 10-20 lobes or reduced to an entire ring; capsule with a prominent apical sterile beak; seeds not borne on hooklike retinacula. |
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4 Thunbergia |
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Prostrate or erect herbs, shrubs, or rarely small trees; calyx 4- or 5-lobed; capsule lacking a prominent apical sterile beak; seeds borne on hooklike retinacula or not |
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(2) |
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| 2 (1) |
Cystoliths absent; retinacula absent (except Acanthus and Blepharis) |
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(3) |
| + |
Cystoliths present; retinacula present, hooklike |
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(7) |
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| 3 (2) |
Seeds laterally compressed, borne on hooklike retinacula; corolla 1-lipped (upper lip absent), lobes not with descending cochlear aestivation; anthers 1-thecous |
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(4) |
| + |
Seeds subspherical or blocky, not borne on hooklike retinacula; corolla 2-lipped, lobes with descending cochlear aestivation; anthers 2-thecous |
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(5) |
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| 4 (3) |
Leaves opposite; flowers not subtended by up to 5 pairs of bracts; seeds lacking hygroscopic trichomes; lower filaments without an apical appendage. |
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5 Acanthus |
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Leaves usually in pseudo-whorl of 4; flowers subtended by up to 5 pairs of bracts; seeds with hygroscopic trichomes; lower filaments with an apical appendage. |
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6 Blepharis |
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| 5 (3) |
Prostrate herbs; bracteoles absent; calyx 4-lobed, anterior lobe 2-cleft at apex; stamens 2. |
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1 Nelsonia |
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Erect herbs; bracteoles present; calyx 5-lobed; stamens 2 or 4 |
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(6) |
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| 6 (5) |
Stamens 4, included or slightly exserted from mouth of corolla; anther thecae of a pair parallel; staminodes 0 or 1. |
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2 Staurogyne |
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Stamens 2, long exserted; anther thecae of a pair divergent toward apex; staminodes 2. |
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3 Ophiorrhiziphyllon |
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| 7 (2) |
Calyx lobes heteromorphic, posterior lobe usually largest, anterior lobes connate to a greater degree than other lobes, lateral lobes smallest and innermost; corolla lobe aestivation quincuncial |
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(8) |
| + |
Calyx lobes homomorphic (or nearly so; sometimes partially fused to form a bipartite or tripartite calyx in Strobilanthes), not as described above; corolla lobe aestivation not quincuncial |
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(10) |
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| 8 (7) |
Corolla large (mostly > 3 cm), upper lip usually appearing 4-lobed and lower lip appearing 1-lobed. |
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29 Barleria |
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Corolla small (< 3 cm), upper lip 2-lobed and lower lip 3-lobed |
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(9) |
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| 9 (8) |
Corolla to 1 cm; anther thecae usually lacking basal appendages; capsule 4-7 mm. |
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30 Lepidagathis |
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Corolla ca. 2.5 cm; anther thecae spurred at base; capsule 12-16 mm. |
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31 Chroesthes |
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| 10 (7) |
Corolla lobes contorted in bud; stamens (or stamens + staminodes) 4 |
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(11) |
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Corolla lobes ascending cochlear in bud; stamens 2 (except 4 in Asystasia), staminodes 0 or 2 |
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(17) |
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| 11 (10) |
Style held in place by trichomes on one side of corolla tube; stamens monadelphous (by a sheath) at base. |
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7 Strobilanthes |
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Style not held in place by trichomes on one side of corolla tube; stamens not monadelphous at base |
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(12) |
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| 12 (11) |
Inflorescence secund strobilate spikes with orbicular to reniform bracts; ovules 2 per locule; seeds to 4 per capsule; corolla ca. 0.6 cm; septa with attached retinacula separating from inner wall of mature capsule. |
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8 Phaulopsis |
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Inflorescence not as described above; ovules 4 to many per locule; seeds 4 or more per capsule; corolla 0.6-5.5 cm; septa with attached retinacula not separating from inner wall of mature capsule (except in Ruellia blechum) |
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(13) |
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| 13 (12) |
Corolla limb distinctly 2-lipped, lobes usually not equal; calyx tube often rupturing in weak hyaline regions between lobes; pollen 4-colporate, interapertural regions multistriate with pseudocolpi. |
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9 Hygrophila |
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Corolla limb nearly regular, lobes equal to subequal; mature calyx tube not rupturing in weak hyaline regions between lobes; pollen otherwise |
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(14) |
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| 14 (13) |
Fertile stamens 2, staminodes 2. |
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10 Eranthemum |
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Fertile stamens 4 |
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(15) |
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| 15 (14) |
Anther thecae spurred at base. |
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11 Echinacanthus |
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Anther thecae muticous at base |
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(16) |
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| 16 (15) |
Stems short; leaves in a basal rosette; anther thecae usually widely separated by a broad connective. |
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12 Pararuellia |
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Stems elongate; leaves cauline; anther thecae not separated by a broad connective. |
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13 Ruellia |
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| 17 (10) |
Ovules 3 to many per locule; seeds 6 to many per capsule; pollen with apertural margins conspicuously thickened |
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(18) |
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Ovules 2 per locule; seeds 4 per capsule; pollen with apertural margins not thickened |
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(21) |
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| 18 (17) |
Capsule compressed perpendicular to septum; seeds subglobose, glabrous. |
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33 Andrographis |
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Capsule linear and 4-angled, not compressed perpendicular to septum; seeds strongly compressed, glabrous or pubescent |
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(19) |
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| 19 (18) |
Staminodes 0. |
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32 Gymnostachyum |
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Staminodes 2 |
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(20) |
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| 20 (19) |
Corolla tube cylindric and slightly curved. |
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34 Phlogacanthus |
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Corolla tube abruptly inflated near middle and usually bent ca. 90°. |
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35 Cystacanthus |
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| 21 (17) |
Stamens 4. |
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14 Asystasia |
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Stamens 2 |
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(22) |
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| 22 (21) |
Anthers 1-thecous |
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(23) |
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Anthers 2-thecous |
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(24) |
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| 23 (22) |
Flowers subtended by a single pair of bracteoles; corolla not resupinate 180° by a twisting of corolla tube (i.e., upper lip entire to 2-lobed and lower lip 3-lobed), or if position of lips reversed then this by geniculation (without twisting) of corolla tube. |
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18 Clinacanthus |
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Flowers subtended by an involucre of 2 or more pairs of floral bracteoles; corolla resupinate 180° by twisting of corolla tube (i.e., lip in upper position 3-lobed and lip in lower position entire to 2-lobed). |
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28 Hypoestes |
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| 24 (22) |
Flowers subtended by involucre of 2 or more pairs of floral bracteoles; corolla resupinate 180° (i.e., lip in upper position 3-lobed and lip in lower position entire to 2-lobed) |
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(25) |
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Flowers subtended by a single pair of bracteoles (or bracteoles rarely lacking); corolla not resupinate 180° (i.e., upper lip entire to 2-lobed and lower lip 3-lobed) |
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(26) |
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| 25 (24) |
Septa with attached retinacula separating from inner wall of mature capsule. |
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26 Dicliptera |
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Septa with attached retinacula remaining attached to inner wall of mature capsule. |
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27 Peristrophe |
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| 26 (24) |
Staminodes 2 |
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(27) |
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Staminodes absent |
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(30) |
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| 27 (26) |
Corolla ± salverform (i.e., tube slender and cylindric, limb spreading and inconspicuously 2-lipped), tube conspicuously longer than limb, not or only slightly widened distally. |
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15 Pseuderanthemum |
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Corolla ± campanulate to strongly 2-lipped (not salverform), tube not longer than limb, gradually widened distally |
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(28) |
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| 28 (27) |
Corolla 3-4 cm; anther thecae 4-5 mm. |
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16 Mackaya |
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Corolla less than 2 cm; anther thecae less than 3 mm |
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(29) |
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| 29 (28) |
Corolla campanulate, 6.5-10 mm, externally glabrous; pollen 4-aperturate. |
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22 Codonacanthus |
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Corolla strongly 2-lipped, 10-15 mm, externally pubescent (to subglabrous); pollen 3-aperturate. |
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23 Cosmianthemum |
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| 30 (26) |
Upper lip of corolla lacking a stylar furrow on internal surface; anther thecae lacking basal appendages |
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(31) |
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Upper lip of corolla rugulate (i.e., with a furrow on inner surface of lip in which style resides); anther thecae (at least lower theca) usually with a basal appendage |
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(33) |
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| 31 (30) |
Corolla 1.7-4.5 cm; anther thecae subequally to unequally inserted; pollen 2-aperturate. |
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17 Isoglossa |
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Corolla less than 10 mm; anther thecae equally to subequally inserted; pollen 3-5-aperturate |
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(32) |
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| 32 (31) |
Corolla glabrous outside. |
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19 Kudoacanthus |
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Corolla pubescent outside. |
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21 Leptostachya |
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| 33 (30) |
Septa with attached retinacula separating from inner wall of mature capsule; inflorescence often dense with imbricate bracts 2- or 4-ranked (but only 2 ranks fertile). |
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20 Rungia |
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Septa with attached retinacula remaining attached to inner wall of mature capsule; inflorescence not as above |
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(34) |
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| 34 (33) |
Corolla not with combination of characters noted below. |
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24 Justicia |
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Corolla white or greenish white, tube narrowly cylindric, conspicuously longer than limb. |
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25 Rhinacanthus |
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List of lower taxa
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