Habit and leaf form. Small trees, or shrubs (with mucilage cells in the cortex). Leaves evergreen; alternate; leathery; petiolate; non-sheathing; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire. Vegetative buds scaly.
Leaf anatomy. Mucilaginous epidermis present. Stomata present; mainly confined to one surface (abaxial); paracytic.
Lamina dorsiventral; without secretory cavities. The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses and solitary-prismatic.
Stem anatomy. Cork cambium present; initially superficial. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids. Vessel end-walls oblique; scalariform. Primary medullary rays mixed wide and narrow. Wood parenchyma apotracheal (diffuse).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes. The ultimate inflorescence unit racemose. Inflorescences terminal and axillary, or intercalary (somewhat); racemes, often with sterile, leafy tips. Flowers (bi-) bracteolate (the persistent bracteoles appressed to the calyx); small; regular; 5 merous (throughout); cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous; regular; persistent; imbricate. Epicalyx absent (but the calyx closely associated with the bracteoles). Corolla 5; 1 whorled; polypetalous; imbricate; regular.
Androecium 5. Androecial members free of the perianth; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous (equalling ir shorter than the petals); alternating with the corolla members; inflexed in bud (later erect); filantherous (the filaments thickened and expanded, especially towards the middle, tapering to their tips, the anthers short). Anthers basifixed; non-versatile; dehiscing via pores (each theca with a terminal pore, opening via a small valve); bilocular (the thecae distinct). Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate (to colporoidate).
Gynoecium 5 carpelled. Carpels isomerous with the perianth. The pistil 5 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 5 locular. Gynoecium stylate. Styles 1; apical; short, stout, persistent. Stigmas 1 (lobed), or 5; if considered one, 5 lobed. Placentation axile to apical. Ovules 2 per locule; pendulous; apotropous (Engler); collateral; somewhat campylotropous, or anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle.
Fruit non-fleshy; partly or fully dehiscent; a capsule (rather woody, with a persistent central axis, cf. Theaceae-Theoideae); without fleshy investment. Capsules loculicidal (to halfway or all the way down, the long-persistent valves with a median septum). Seeds scantily endospermic; more or less winged. Embryo well differentiated. Cotyledons 2. Embryo curved (horseshoe-shaped).
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Aluminium accumulation demonstrated.
Geography, cytology. Paleotropical. Tropical. South China to Malay Peninsula and Sumatra.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Theiflorae (?); Theales (?). Cronquist’s Subclass Dilleniidae; Theales. APG 3 core angiosperms; core eudicot; Superorder Asteranae (but this conflicts with the embryology as reported by Davis, 1966); Order Ericales.
Species 1–2. Genera 1; only genus, Pentaphylax.