Dilleniaceae Salisb.

Shrubs, lianas, trees or rarely perennial herbs (not in Australia), glabrous or with a vestiture of unicellular trichomes comprising simple to fasciculate hairs which may be modified into fimbriate peltate scales and are sometimes borne on rounded to elongate tubercles. Stems ± terete or rarely flattened into cladodes. Leaves alternate and spirally arranged or rarely opposite (not in Australia), petiolate or sessile (rarely perfoliate or amplexicaul), rarely with the adult leaves apparently absent or reduced and scale-like; lamina simple or rarely pinnatisect to pinnate (not in Australia), sometimes sclerophyllous, exstipulate (the petioles rarely with persistent or caducous amplexicaul wings); lamina entire or rarely toothed or lobed, terete to flat, with margins flat to tightly recurved or revolute to the midrib, rarely involute; venation usually pinnate (often obscure in Hibbertia), often with ± straight parallel secondary veins (which sometimes terminate in teeth or lobes), sometimes with reticulate tertiary venation, sometimes festooned-brochidodromous; apex rounded to attenuate, rarely truncate or emarginate, sometimes with the excurrent midrib hard and pungent. Inflorescence determinate, terminal, leaf-opposed or axillary (rarely ramiflorous), comprising a solitary flower or with few to many flowers borne in cymose inflorescences or in branched or unbranched pseudo-cincinnae. Bracts absent to many, subtending the flowers or pedicels, herbaceous to scarious. Flowers usually actinomorphic or sometimes (mainly in the androecium) zygomorphic, hypogynous or very rarely partly epigynous, bisexual (rarely plants androdioecious), small to very large. Sepals (2­) 3–5 (–18), equal to subequal, usually free except at the base, quincuncial, persistent, usually ± accrescent. Petals (1–) 3–5 (–7) or very rarely absent (not in Australia), free, imbricate, elliptic to obovate and often emarginate, usually yellow (rarely white, orange, pink or red), deciduous. Stamens 1–numerous, in a complete to interrupted ring or in 2–5 groups around the carpels (rarely obdiplostemonous) or in a group to one side of the carpels, usually free or with the filaments basally to nearly fully connate; anthers 2-locular, basifixed, opening by longitudinal slits or apical pores; staminodes present or absent. Gynoecium of 1–10 (–20) usually free or less frequently basally connate carpels, in 1 to rarely 2 whorls; styles free, stigma simple, minute to slightly peltate; ovules 1–80; placentation marginal with ovules in 2 (4 or 6) vertical rows or basal when ovules 1 or 2. Fruit usually a dehiscent follicle or aggregate of follicles, or indehiscent and enclosed by the fleshy accrescent sepals, rarely a fleshy capsule, berry or aggregate of nutlets. Seeds arillate, the aril fleshy to scarious, oily or waxy, white or orange to red, funicular; seed coat with endotesta typically heavily sclerotized or sometimes cutinized; endosperm fleshy, oily or sometimes also starchy, abundant; embryo small, straight, sometimes scarcely developed at seed shed.

In Australia, the genera Dillenia and Tetracera occur in rainforests, while Hibbertia are mostly found in temperate to monsoon-tropical shrublands, woodlands and forests, with very few in alpine or desert regions.

Species of Dillenia have been widely used in folk medicine to treat cancers, wounds, jaundice, fever, cough, diabetes mellitus and diarrhoea, and as hair tonics. Some species have edible fruits and some are cultivated as ornamentals. Flavonoids, triterpenoids and miscellaneous other pharmacologically active compounds have been identified in Dillenia. (Sabandar et al. 2016). Some species of Hibbertia are popular in cultivation as ornamentals, particularly the climber or sprawling ground cover H. scandens (Willd.) Dryand. with its showy bright yellow flowers.