Isolona Engl.

Trees or treelets up to 30 m tall; young branches densely covered with erect or appressed hairs to glabrous. Petioles 1-15 mm long, leaf lamina inserted on side or on top, broadly to narrowly grooved adaxially. Leaf lamina elliptic to ovate or obovate, base decurrent to rounded, apex acute to acuminate, papyraceous to coriaceous; midrib raised adaxially, prominent abaxially; secondary veins 6-20 pairs, straight or uniformally curving upwards, loop forming towards margin; tertiary veins intermediate between reticulate and percurrent. Flowers bisexual, regular. Inflorescence a single, axillary, 1-flowered or rarely many-flowered rhipidium, occasionally one or two additional rhipidia are present, growing on leafy branches, older leafless branches or on the trunk. Flowering pedicels variable in size and slender. Lower bracts 2-6, minute. Upper bract present, variable in size, or sometimes absent. Sepals 3, valvate, free, ovate to broadly ovate, margins straight. Petals 6, clearly fused at base into a tube shorter than or rarely longer than the corolla lobes; tube urceolate or not; corolla lobes spreading horizontally or vertically, linear to elliptic, coriaceous to papyraceous, rarely membranous; yellow to red at anthesis. Receptacle slightly convex. Stamens short and broad, glabrous, shielded by a truncate and broadened apical prolongation of the connective, which can be glabrous or hairy; anthers with extrorse dehiscence; pollen in monads, inaperturate. Carpels 5-6, congenitally fused into a syncarpous ovary; stigma capitate, bilobed; ovules numerous, biseriate; placentation parietal. Fruiting pedicels thick and woody to slender. Fruits syncarpous, globose to conical. Pericarp thick and woody to thin. Seeds numerous, ellipsoid to broadly ellipsoid; testa smooth or rugose; raphe thickened or flat; hilum elliptical to oblong; rumination lamellate in four parts. Base chromosome number n=8.