The families of flowering plants.
IncludingHalesiaceae D. Don, Styraceae (Styracaceae) Spreng. (p.p.)
Habit and leaf form. Trees and shrubs; resinous. ‘Normal’ plants. Leaves alternate; ‘herbaceous’, or leathery; petiolate; without marked odour; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire, or crenate, or serrate, or dentate.
Leaf anatomy. Stomata present; mainly confined to one surface (abaxial); anomocytic. Hairs present; multicellular. Complex hairs usually present (usually brown or rufous); peltate, or stellate.
Lamina dorsiventral. Minor leaf veins without phloem transfer cells (Styrax).
Stem anatomy. Secretory cavities present, or absent; when present, with resin. Cork cambium present; initially deep-seated. Nodes unilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. Xylem with fibre tracheids; with vessels. Vessel end-walls scalariform, or scalariform and simple. Wood parenchyma apotracheal (usually), or paratracheal (scanty and diffuse, rarely).
Reproductive type, pollination. Plants hermaphrodite (usually), or polygamomonoecious (Bruinsmia).
Inflorescence, floral, fruit and seed morphology. Flowers solitary (occasionally), or aggregated in ‘inflorescences’; in cymes, or in racemes, or in panicles. Inflorescences terminal, or axillary. Flowers ebracteolate;regular; cyclic; tetracyclic. Free hypanthium present, or absent.
Perianthwith 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; not appendiculate; polypetalous (rarely, Bruinsmia, but often almost so), or gamopetalous (generally with the tube much shorter than the lobes, rarely (Halesia) these shorter than the tube). Corolla lobes markedly longer than the tube (usually), or markedly shorter than the tube (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, 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. Gynoeciumsyncarpous; eu-syncarpous; superior to inferior. Ovary (2–)3–5 locular. Gynoecium stylate. Styles 1; apical. Stigmas1 (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.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (3 species). Iridoids not detected. Proanthocyanidins present, or absent; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (2 genera, 2 species). Saponins/sapogenins present. Aluminium accumulation not found. Sugars transported as sugar alcohols + oligosaccharides + sucrose (in Styrax, but sucrose predominating).
Geography, cytology. Temperate (warm), or 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 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.
Species 180. Genera 11; Alniphyllum, Bruinsmia, Halesia, Huodendron,Melliodendron, Pamphilia, Parastyrax, Pterostyrax, Rehderodendron,Sinojackia, Styrax.