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The families of flowering plants

L. Watson and M.J. Dallwitz

Styracaceae Dum.

Including Halesiaceae D. Don, Styraceae (Styracaceae) Spreng. (p.p.).

Habit and leaf form. Trees and shrubs; resinous. ‘Normal’ plants. Leaves alternate; ‘herbaceous’, or leathery; petiolate; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire, or crenate, or serrate, or dentate.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; mainly confined to one surface (abaxial); anomocytic. Hairs present (often with a conspicous indumentum of stellate or scale-like hairs); multicellular. Complex hairs usually present (usually brown or rufous); peltate, or stellate. Minor leaf veins without phloem transfer cells (Styrax).

Axial (stem, wood) anatomy. Secretory cavities present, or absent; when present, with resin. Cork cambium present; initially deep-seated. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles. Secondary thickening developing from a conventional cambial ring. Primary medullary rays mixed wide and narrow, or narrow.

The wood semi-ring porous, or diffuse porous. The vessels small to medium; solitary, radially paired, and in radial multiples. The vessel end-walls scalariform, or scalariform and simple. The vessels without vestured pits; without spiral thickening. The axial xylem with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal (usually), or paratracheal (scanty and diffuse, rarely); wood not storied.

Reproductive type, pollination. Plants hermaphrodite (usually), or polygamomonoecious (Bruinsmia).

Inflorescence, floral, fruit and seed morphology. Flowers solitary (occasionally), or aggregated in ‘inflorescences’; usually in cymes, or in racemes, or in panicles. Inflorescences terminal, or axillary. Flowers ebracteolate; regular; cyclic; tetracyclic. Free hypanthium present, or absent.

Perianth with distinct calyx and corolla; (4–)8–10(–14); 2 whorled; isomerous. Calyx (2–)4–5(–7); 1 whorled; gamosepalous; entire, or lobulate, or blunt-lobed, or toothed; tubular; regular; persistent; valvate, or open in bud. Corolla (2–)4–5(–7); 1 whorled; polypetalous (rarely absolutely so, as in Bruinsmia, but often almost so), or gamopetalous. Corolla lobes markedly longer than the tube (usually), or markedly shorter than the tube (in Halesia). Corolla imbricate, or valvate; not fleshy.

Androecium (5–)8–10(–20) (commonly twice as many as the corolla lobes, sometimes four times as many). Androecial members adnate (the filaments adnate to the corolla tube), or free of the perianth (rarely, then attached directly to the receptacle); free of one another (rarely), or coherent (usually,below, into a short to long tube); usually 1 adelphous; 1 whorled. Androecium exclusively of fertile stamens. Stamens (5–)8–10(–20); isomerous with the perianth (Pamphilia), or diplostemonous to polystemonous (but all in one whorl); when 5, oppositisepalous. Anthers adnate; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate; appendaged (sometimes, the connective shortly prolonged), or unappendaged. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate (colpor(oid)ate, constricticolpate); 2-celled.

Gynoecium (2–)3–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil (2–)3–5 celled. Gynoecium syncarpous; eu-syncarpous; superior to inferior. Ovary (2–)3–5 locular. Gynoecium stylate. Styles 1; apical. Stigmas 1 (capitate or merely lobed). Placentation axile. Ovules (1–)4–6(–50) per locule; pendulous to ascending; sometimes with an obturator; anatropous, or hemianatropous; unitegmic (Halesia), or bitegmic (Styrax); tenuinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing only after one has been fertilized. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids elongated. Endosperm formation cellular. Embryogeny solanad.

Fruit fleshy (rarely), or non-fleshy; dehiscent, or indehiscent; a capsule, or capsular-indehiscent, or a drupe (rarely), or a samara; one- or few-seeded. Seeds endospermic. Endosperm oily. Seeds winged (Alniphyllum), or wingless. Embryo well differentiated. Cotyledons 2; flat (broad). Embryo achlorophyllous (2/2); slightly curved, or straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Sugars transported as sugar alcohols + oligosaccharides + sucrose (in Styrax, but sucrose predominating). Not cyanogenic. Alkaloids absent (3 species). Iridoids not detected. Saponins/sapogenins present. Proanthocyanidins present, or absent; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (2 genera, 2 species). Aluminium accumulation not found.

Geography, cytology. Temperate (warm), sub-tropical to tropical. Eastern Asia to Western Malaysia, Mediterranean, Southeast U.S.A., Mexico to tropical South America. X = 8, 12.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Primuliflorae; Ebenales. Cronquist’s Subclass Dilleniidae; Ebenales. APG III core angiosperms; core eudicot; Superorder Asteranae. APG IV Order Ericales.

Species 180. Genera 11; Alniphyllum, Bruinsmia, Halesia, Huodendron, Melliodendron, Pamphilia, Parastyrax, Pterostyrax, Rehderodendron, Sinojackia, Styrax.

Illustrations. • Le Maout and Decaisne: Styrax officinalis. • Styrax suberifolium and S. leiophylla, Halesia tetraptera: Lindley. • Halesia cardina: Bot. Reg. 952, 1825. • Alniphyllum pterospermum: Hook. Ic. Pl. 28 (1905).

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.’.