Habit and leaf form. Herbs; probably bearing essential oils; resinous. Leaves deciduous; alternate; petiolate; non-sheathing; aromatic; compound; impari- pinnate. Lamina pinnately veined; cross-venulate. Leaves stipulate. Stipules caducous (small). Lamina margins denticulate.
Leaf anatomy. Stomata present; anomocytic. Hairs present; eglandular and glandular. Complex hairs present; peltate (basally embedded, glandular).
Lamina without secretory cavities. The mesophyll without etherial oil cells.
Stem anatomy. Secretory cavities absent. Cork cambium present. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with vessels. Vessel end-walls oblique; scalariform. Wood parenchyma mostly paratracheal (vasicentric).
Reproductive type, pollination. Plants hermaphrodite, or gynomonoecious (the flowers hermaphrodite and female (?), hermaphrodite and sterile, or the reduced members abortive). Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in catkins. The ultimate inflorescence unit cymose (the flowers in bracteate dichasial triplets, the central member of each triplet hermaphrodite, the laterals pistillate but (usually or always?) sterile, or abortive). Inflorescences aments of dichasial triplets, clustered into large, nodding, terminal panicles. Flowers small (and inconspicuous). Free hypanthium absent. Hypogynous disk absent.
Perianth of the perfect flowers sepaline (the corolla absent); 4; 2 whorled (2+2); isomerous; persistent. Calyx 4; 2 whorled (2+2); polysepalous (the sepals small, scarious); persistent; non-accrescent; imbricate.
Androecium of the hermaphrodite flowers 6. Androecial members free of the perianth; free of one another. Androecium exclusively of fertile stamens. Stamens 6; shortly filantherous (the filaments persistent). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; bilocular; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3(–4) aperturate; colporate (with short colpi and large pores).
Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synovarious; superior. Ovary 2 locular (below, but unilocular above, the partition falling short of the top). Gynoecium stylate. Styles 2; free; apical. Stylar canal present. Stigmas 2. Placentation axile. Ovules 1 per locule (but in only one locule of each pair, the other being sterile); ascending; hemianatropous to anatropous; bitegmic; crassinucellate. Endosperm formation nuclear.
Fruit non-fleshy; indehiscent; a samara (a two-winged, samaroid nut); 1 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2 (thick, oily). Embryo straight.
Physiology, biochemistry. Aluminium accumulation not found.
Geography, cytology. Paleotropical. Sub-tropical to tropical. Southern China, Indochina.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Juglandales (cf. Juglandaceae). Cronquist’s Subclass Hamamelidae; Juglandales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Fagales (as a synonym of Juglandaceae?).
Species 1. Genera 1; only genus, Rhoiptelea.