Family Sometimes included in Liliaceae.
Habit and leaf form. Herbs, or herbaceous climbers. Perennial; plants with neither basal nor terminal concentrations of leaves; rhizomatous and tuberous (some of the roots being modified to store water and nutrients). Self supporting, or climbing; when climbing, stem twiners. Mesophytic. Leaves medium-sized; alternate; spiral; petiolate; non-sheathing; simple. Leaf blades generally inverted; entire; flat; linear to lanceolate; parallel-veined; without cross-venules; attenuate at the base. Leaf blade margins entire. Leaf anatomy. Guard-cells not ‘grass type’. Stem anatomy. Secondary thickening absent. Roots. Roots without velamen.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the perianth (from the bases of two or all of the inner tepals).
Inflorescence and flower features. Flowers solitary (rarely), or aggregated in ‘inflorescences’; in cymes, or in umbels. The terminal inflorescence unit cymose. Inflorescences terminal; umbelliform, helicoid cymes. Flowers bracteate (the bracts leaflike); medium-sized; regular to somewhat irregular; sometimes slightly zygomorphic; 3 merous; cyclic; pentacyclic. Perigone tube absent (3+3). Perianth with distinct calyx and corolla, or of ‘tepals’; 6; 2 -whorled; isomerous; mostly free; petaloid, or sepaloid and petaloid; spotted; similar in the two whorls to different in the two whorls (the outer whorl often shorter, of different colour and less variegated); green, or orange, or red, or pink; deciduous. Androecium 6. Androecial members free of the perianth; free of one another; 2 -whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; diplostemonous; alterniperianthial. Anthers (pseudo-) basifixed, or dorsifixed; non-versatile; dehiscing via longitudinal slits; introrse. Pollen shed as single grains. Gynoecium 3 carpelled. The pistil 1 celled, or 3 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; synstylovarious; superior. Ovary unilocular (rarely), or plurilocular; 1 locular, or 3 locular. Styles 1; apical. Stigmas 3; wet type. Placentation when unilocular, parietal; when trilocular, axile. Ovules in the single cavity 20–100 (‘many’); 20–100 per locule (‘many’); non-arillate; anatropous.
Fruit and seed features. Fruit fleshy (sometimes), or non-fleshy; dehiscent (usually, occasionally explosively so), or indehiscent; a capsule (usually), or capsular-indehiscent, or a berry. Capsules when dehiscent, loculicidal. Fruit elastically dehiscent, or passively dehiscent. Seeds endospermic. Endosperm oily. Seeds without starch. Embryo well differentiated. Cotyledons 1 (not coleoptile-like). Embryo straight. Testa without phytomelan. Seedling. Hypocotyl internode present. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated, or compact; assimilatory, or non-assimilatory. Coleoptile absent. Seedling cataphylls present. First leaf dorsiventral. Primary root persistent.
Geography, cytology, number of species. Neotropical and Antarctic. World distribution: Central and South America. X = 8, 9. 200 species.