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The families of flowering plants

L. Watson and M.J. Dallwitz

Strychnaceae Link.

~ Loganiaceae.

Excluding Antoniaceae.

Habit and leaf form. Trees (to 40 m), or shrubs, or lianas; non-laticiferous, without coloured juice. Self supporting, or climbing; the climbers tendril climbers, or scrambling (spiny or prickly). Mesophytic, or xerophytic. Leaves opposite, or whorled; when whorled, 3 per whorl; ‘herbaceous’, or leathery (commonly, in Strychnos); petiolate, or subsessile; connate, or not connate; simple. Lamina entire; pinnately veined, or palmately veined; cross-venulate. Leaves stipulate, or exstipulate (stipules in Strychnos often represented only by an interpetiolar ridge). Stipules interpetiolar, or intrapetiolar; free of one another, or concrescent (Strychnos sect. Spinosae exhibiting ‘normal’, free stipules); ochreate (Neubergia), or not ochreate; with colleters. Leaf development not ‘graminaceous’. Domatia occurring in the family; manifested as pockets, or hair tufts.

Leaf anatomy. Hairs present, or absent; eglandular. Complex hairs absent. The mesophyll with sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Strychnos).

Axial (stem, wood) anatomy. Internal phloem present. Secondary thickening anomalous. The anomalous secondary thickening from a single cambial ring. Primary medullary rays mixed wide and narrow (uniseriate and multiseriate).

The wood ring porous, or diffuse porous. The vessel end-walls generally horizontal (or almost so), or horizontal to oblique (e.g., in Neuburgia); seemingly always simple. The vessels with vestured pits. The axial xylem commonly with tracheids; with fibre tracheids (usually), or without fibre tracheids (e.g. in Sect. Spinosae); with libriform fibres, or without libriform fibres; seemingly always without septate fibres. The parenchyma usually present, apotracheal, or paratracheal, or apotracheal and paratracheal. ‘Included’ phloem present. Tile cells present (e.g. Neuburgia?), or absent. The wood not storied.

Reproductive type, pollination. Plants hermaphrodite; homostylous. Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually), or solitary; in cymes, or in corymbs, or in panicles. The ultimate inflorescence units cymose. Inflorescences cymes or corymbose-paniculate. Flowers bracteate (bracts small); regular; 4–5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 8, or 10; 2 whorled; isomerous. Calyx 4–5; 1 whorled; polysepalous, or gamosepalous; unequal but not bilabiate, or regular; imbricate. Epicalyx absent. Corolla 1–5; 1 whorled; gamopetalous (the tube short); valvate; regular; green, or white, or yellow, or orange (or membranous); fleshy.

Androecium 4–5. Androecial members adnate; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4–5; inserted midway down the corolla tube, or in the throat of the corolla tube; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers separate from one another, or connivent (Gardneria); dorsifixed, or dorsifixed to basifixed (?); dehiscing via longitudinal slits; introrse; bilocular (usually), or four locular (some Gardneria species); appendaged (Neubergia), or unappendaged. The anther appendages when present, apical, or apical and basal. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Tapetum glandular. Pollen grains aperturate; (2–)3(–4) aperturate; colporate (rarely syncolpate); 3-celled.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2 locular. Gynoecium median; stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1 lobed, or 2 lobed; more or less capitate. Placentation axile. Ovules (1–)2–50 per locule (to ‘many’); non-arillate; anatropous; unitegmic; tenuinucellate. Endothelium not differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Hypostase absent. Endosperm formation nuclear. Embryogeny onagrad.

Fruit indehiscent; a berry, or a drupe (sometimes large). Seeds endospermic. Embryo straight.

Physiology, phytochemistry. Not cyanogenic. Alkaloids present. Iridoids detected; ‘Route I’ type (plus complex indole alkaloids). Saponins/sapogenins present, or absent. Proanthocyanidins absent. Ellagic acid absent. Aluminium accumulation demonstrated.

Geography, cytology. Sub-tropical to tropical. Pantropical and subtropical. 2n = 44, 88, 110. Supposed basic chromosome number of family: 11. Ploidy levels recorded: 4, 8, and 10.

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 250. Genera 4; Strychnos, Scyphostrychnos, Gardneria, Neubergia.

General remarks. Leeuwenberg 1980, under Loganiaceae. Struwe et al. (1994) include Antoniaceae and Spigelia here, but the present compilation of data suggests Strychnaceae are somewhat closer to Gentianaceae, Potaliaceae and Loganiaceae sensu stricto (cf. APG). It has them differing conspicuously from Loganiaceae sensu stricto (q.v.) only in the fleshy, valvate corolla and fruit types, but also in ‘esoteric characters’ depending on limited sampling (vessels with vestured pits, cytology). See further comments under Loganiaceae.

Illustrations. • Strychnos ligustrina, cf. S. nux-vomica: Lindley. • Strychnos ignatii: Hook. Ic. Pl. 23 (1894). • cf. Strychnos potatorum: R. Wight 2 (1850).

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: 15th April 2018.’.