Habit and leaf form. Tall trees. Leaves evergreen; opposite (usually), or whorled (less often); when whorled 3 per whorl; petiolate; not gland-dotted; simple (rarely), or compound; when compound, unifoliolate, or ternate, or pinnate. Lamina pinnately veined; cross-venulate. Leaves stipulate (and stipellate). Stipules caducous (small). Lamina margins entire, or dentate (sometimes doubly dentate).
Leaf anatomy. Extra-floral nectaries absent (commonly), or present. Stomata present; anomocytic. Hairs present; unicellular.
Adaxial hypodermis present. Lamina dorsiventral.
Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with vessels. Vessel end-walls oblique; simple, or scalariform and simple. Primary medullary rays mixed wide and narrow, or narrow. Wood parenchyma wanting.
Reproductive type, pollination. Plants hermaphrodite, or dioecious, or gynodioecious. Female flowers with staminodes, or without staminodes (androecium vestigial). Gynoecium of male flowers vestigial.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes and in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary; branching cymes. Flowers small; regular; cyclic. Free hypanthium absent. Hypogynous disk present (adnate to the calyx); intrastaminal; annular (hairy, notched).
Perianth sepaline; (4–)5(–8); 1 whorled. Calyx (4–)5(–8); 1 whorled; gamosepalous (shortly connate below); 4–8 blunt-lobed. Calyx lobes markedly longer than the tube. Calyx regular; persistent; valvate.
Androecium 8–10(–14). Androecial members branched (in that the members of the inner, antesepalous set are sometimes paired, and up to twice as many as in the outer set), or unbranched; free of the perianth; free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens 8–10(–14); diplostemonous to triplostemonous; alternisepalous; filantherous (the filaments hairy). Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse. Pollen grains aperturate; 3 aperturate; colporate.
Gynoecium (2–)4–5(–8) carpelled; apocarpous; eu-apocarpous; superior. Carpel stylate; apically stigmatic (the style slender, elongate, recurved or almost circinnate, the stigma decurrent along its sulcus); 2 ovuled. Placentation marginal (the ovules near the middle of the ventral suture). Ovules pendulous; epitropous; collateral; non-arillate; anatropous; bitegmic; presumed crassinucellate.
Fruit non-fleshy; an aggregate. The fruiting carpel dehiscent; a follicle (with a dense, short reddish to yellowish indumentum, plus longer, straight, lignified, pointed hairs. Each follicle becoming abaxially distorted to bring the style outwards or downwards). Seeds copiously endospermic. Embryo well differentiated (large). Cotyledons 2 (flattened). Embryo straight. Micropyle not zigzag.
Seedling. Germination phanerocotylar.
Geography, cytology. Neotropical. Tropical. America.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Cunoniales. Cronquist’s Subclass Rosidae; Rosales. APG (1998) Eudicot; core Eudicot; Rosid; Eurosid I. APG 3 (2009) Order: Oxalidales.
Species 45. Genera 1; only genus, Brunellia.