Habit and leaf form. Scandent herbs (with turniplike rootstock). Perennial. Climbing; stem twiners. Leaves alternate; flat; long petiolate (the petioles twisted near the base); non-sheathing; simple. Lamina entire; ovate; pinnately veined; cross-venulate; cordate. Leaves exstipulate. Lamina margins entire.
Leaf anatomy. Stomata present; anomocytic.
Stem anatomy. Secondary thickening anomalous (with successive rings of vascular bundles). Sieve-tube plastids P-type; type III (a).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence unit cymose (cymules). Inflorescences loose, axillary; panicles of cymules. Flowers bracteate; bracteolate; fragrant. Free hypanthium absent.
Perianth sepaline (corolla absent); 4(–5); 1 whorled. Calyx 4(–5); 1 whorled; polysepalous; regular; persistent; accrescent (these becoming stellately and reticulately veiny in the fruit).
Androecium 15–20. Androecial members free of the perianth (inserted on a thin perigynous disk); all equal; free of one another; ‘in more than one series’. Androecium exclusively of fertile stamens. Stamens 15–20; triplostemonous to polystemonous; filantherous (the filaments filiform). Anthers dorsifixed (oblong, bifid at each end); dehiscing via longitudinal slits.
Gynoecium (3–)4 carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil (3–)4 celled. Gynoecium syncarpous; synstylovarious; partly inferior. Ovary (3–)4 locular. Gynoecium stylate. Styles 1; apical; shorter than the ovary (short, conical). Stigmas 3–4 (recurved). Placentation basal to axile. Ovules 1 per locule; funicled; hemianatropous.
Fruit non-fleshy; indehiscent; achene-like (turbinate, unilocular by abortion, the leathery pericarp adherent to the seed, winged by the persistent, dry calyx); 1 seeded. Seeds probably non-endospermic. Perisperm presumably present (represented by ‘thin, mealy endosperm’). Embryo well differentiated. Cotyledons 2. Embryo curved (more or less annular).
Physiology, biochemistry. Alkaloids absent. Iridoids not detected. Proanthocyanidins absent.
Geography, cytology. Neotropical. Tropical. Central America and tropical South America.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG (1998) Eudicot; core Eudicot; neither Rosid nor Asterid. APG 3 (2009) Order: Caryophyllales.
Species 1. Genera 1; only genus, Agdestis.