Habit and leaf form. Lianas (usually), or shrubs. Climbing (usually), or self supporting (less often). Leaves alternate; ‘herbaceous’, or leathery; petiolate; non-sheathing; with minute, obscure reddish gland-dots, cf. Myrsinaceae; simple. Lamina entire; pinnately veined (the laterals usually arcuate-anastomosing). Leaves exstipulate. Lamina margins entire (usually cartilaginous).
Leaf anatomy. Stomata present; anomocytic, or paracytic.
Lamina dorsiventral; without secretory cavities. The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses.
Stem anatomy. Secretory cavities absent. Cork cambium present; initially superficial. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids, or without tracheids (?); with fibre tracheids (Metcalfe and Chalk 1965, the fibres sometimes septate); without libriform fibres; with vessels. Vessel end-walls scalariform, or simple, or reticulately perforated. Primary medullary rays wide, or mixed wide and narrow.
Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes, or in panicles. Inflorescences axillary; usually few- to many-flowered pedunculate cymes, rarely a small panicle or a simple raceme. Flowers minute, or small; regular; (4–)5(–6) merous; cyclic; tetracyclic. Hypogynous disk present; intrastaminal; annular (or cupular), or of separate members (the lobes sometimes bearing indurated, more or less discoid glands).
Perianth with distinct calyx and corolla; (8–)10(–12); 2 whorled; isomerous. Calyx (4–)5; 1 whorled; polysepalous; imbricate. Corolla (4–)5(–6); 1 whorled; opposite the calyx; polypetalous (the petals opposite the sepals, larger); imbricate; fleshy, or not fleshy.
Androecium (4–)5(–6). Androecial members adnate (to the bases of the petals); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens (4–)5(–6); isomerous with the perianth; oppositisepalous (but also opposite the petals, which are themselves opposite the sepals); alternating with the corolla members. Anthers extrorse, or introrse. Anther wall initially with more than one middle layer (2). Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate (to colporoidate).
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary 2 locular. Gynoecium stylate. Styles 2; partially joined (erect, more or less coherent); apical to lateral. Stigmas 2 (simple). Placentation axile to apical. Ovules 2 per locule; horizontal to ascending; more or less apotropous; with ventral raphe; collateral, or superposed; hemianatropous; unitegmic (the single integument not covering the dome-shaped nucellus, so forming no micropyle); crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked. Endosperm formation helobial. Endosperm haustoria present; chalazal.
Fruit fleshy (with crustaceous, conspicuously sculptured or pitted endocarp); indehiscent, or a schizocarp. Mericarps when schizocarpic, 2; comprising drupelets (flattened, dorsally gibbous drupaceous carpels, their styles becoming adaxially subbasal and persisting as a beak on each carpel). Fruit if non-schizocarpic, a drupe. Seeds non-endospermic. Cotyledons 2 (oily).
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present. Flavonols present; quercetin, or kaempferol and quercetin (?). Aluminium accumulation not found.
Geography, cytology. Paleotropical. Sub-tropical to tropical. India and Eastern Asia to the Solomons. 2n = 24.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae (? — tentatively re-assigned from Rutiflorae, cf. Chase et al 1993); near Hamamelidales (?). Cronquist’s Subclass Magnoliidae; Ranunculales. APG 3 core angiosperms; peripheral eudicot; cf. Superorder Proteanae; Order Sabiales.
Species 55. Genera 1; only genus, Sabia.