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The families of flowering plants

L. Watson and M.J. Dallwitz

Antoniaceae (Endl.) J.G. Agardh

~ Loganiaceae sensu lato, Strychnaceae.

Habit and leaf form. Small to large trees, or shrubs, or lianas; non-laticiferous. Self supporting, or climbing. Mesophytic. Leaves opposite; petiolate; connate, or not connate; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate (in the form of a short sheath), or exstipulate (then the stipules represented by a ciliolate rim, or an interpetiolar line). Stipules interpetiolar; with colleters (often), or without colleters. Lamina margins entire, or dentate. Leaf development not ‘graminaceous’.

Leaf anatomy. Hairs present, or absent; when present, eglandular. Complex hairs absent (glabrous or with simple hairs).

Axial (stem, wood) anatomy. Primary vascular tissues bicollateral. Internal phloem present. Secondary thickening anomalous. The anomalous secondary thickening from a single cambial ring. Primary medullary rays narrow (usually), or wide (Usteria).

The wood diffuse porous. The vessel end-walls oblique; simple. The vessels with vestured pits. The axial xylem with tracheids (abundant, in Usteria), or without tracheids; with fibre tracheids (Usteria), or without fibre tracheids (the rest); with libriform fibres (mostly), or without libriform fibres (Usteria). The parenchyma apotracheal (mostly), or apotracheal and paratracheal (Usteria). ‘Included’ phloem of the foraminate type present. Tile cells present (e.g., Usteria), or absent. The wood not storied.

Reproductive type, pollination. Plants hermaphrodite; homostylous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in panicles. The ultimate inflorescence units cymose. Inflorescences terminal (usually), or terminal and axillary (Norrisia); several to many flowered, repeatedly dichasially branched to thyrsoid. Flowers bracteate; bracteolate; regular to somewhat irregular (usually regular except for the sometimes unequal sepals), or very irregular (Usteria); of Usteria zygomorphic. The floral irregularity involving the perianth, or involving the perianth and involving the androecium. Flowers 5 merous (usually), or 4 merous (Usteria); cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk small or absent.

Perianth with distinct calyx and corolla; 8–10; 2 whorled; isomerous. Calyx 4–5; 1 whorled; polysepalous, or gamosepalous; unequal but not bilabiate (having one lobe enlarged or petaloid), or regular; persistent; non-accrescent; imbricate, or valvate, or open in bud. Corolla 4 (Usteria), or 5 (usually); 1 whorled; gamopetalous (usually hairy inside). Corolla lobes markedly shorter than the tube, or about the same length as the tube. Corolla valvate; hypocrateriform, or tubular (the tube often slender); regular; white (or cream), or yellow, or pink, or purple, or blue (or violet, or mauve); fleshy, or not fleshy.

Androecium 5 (usually), or 1 (Usteria). Androecial members adnate (inserted at the mouth of the corolla tube); all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5 (usually), or 1 (Usteria); inserted in the throat of the corolla tube; reduced in number relative to the adjacent perianth (Usteria), or isomerous with the perianth; oppositisepalous (the single stamen of Usteria inserted between the larger pair of corolla lobes); alternating with the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits; latrorse, or introrse. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior (nearly always), or partly inferior (rarely). Ovary 2 locular. Gynoecium stylate. Styles 1 (deciduous or persistent); apical. Stigmas 1 (unbranched); 1 lobed, or 2 lobed. Placentation axile (the placental stalk central). Ovules 15–50 per locule (‘many’); anatropous, or amphitropous; tenuinucellate.

Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal. Fruit 1–50 seeded (to ‘many’). Seeds endospermic (the endosperm fleshy or starchy); winged (the wing diaphanous, reticulate-veined). Embryo straight, or curved.

Physiology, phytochemistry. Alkaloids absent (or only traces present). Verbascosides not detected. Cornoside not detected. Iridoids not detected. Aluminium accumulation demonstrated (in Antonia ovata).

Geography, cytology. Tropical. ‘Tropics’. 2n= 22 (only Usteria screened. Supposed basic chromosome number of family: 11. Ploidy levels recorded: 2.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Gentianiflorae; Gentianales. Cronquist’s Subclass Asteridae; Gentianales. APG III core angiosperms; core eudicot; Superorder Asteranae; lamiid. APG IV Order Gentianales (as a synonym of Loganiaceae).

Species 8. Genera 4; Antonia, Bonyunia, Norrisia, Usteria.

General remarks. See Leeuwenberg 1980, under Loganiaceae. Associated with Strychnaceae via cladistic analyses by Struwe et al (1994), but in terms of the data compiled for the present package, apart from differences in characters relying on limited sampling (wood anatomical, iridoids, basic chromosome number) they differ from Loganiaceae (q.v.) only in the the valvate corolla and winged seeds, and from Gentianaceae only in the valvate corolla. See further comments under Loganiaceae.

Illustrations. • Antonia pilosa: Hook. Ic. Pl. 1 (1837). • Antonia ovata (Hutchinson).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 5th March 2018.’.