Herbs or lianas [shrubs, rarely trees], deciduous or evergreen, often aromatic. Wood with broad medullary rays. Leaves alternate, simple, petiolate. Leaf blade unlobed, margins entire. Inflorescences terminal or axillary, racemes or solitary flowers, rarely fan-shaped cymes. Flowers bisexual; calyx enlarged, petaloid, usually tubular, [1-,] 3-, [6-, rarely 5-]merous, lobes valvate; corolla usually reduced to scales or absent; stamens 5, 6, or 12 [multiples of 3 or 5], free or adnate to styles and stigmas, forming gynostemium; anthers extrorse; pistil 1, 4-6-carpellate; ovary inferior, partly inferior, or superior; placentation axile (and ovaries 4-6-locular) or parietal; ovules many per locule, anatropous. Fruits capsules [follicles], regularly to irregularly loculicidal, rarely indehiscent [septicidal]. Seeds often flattened; endosperm copious.
PLANT: Perennial herbs, shrubs or often vines. LEAVES: alternate, simple; stipules absent. INFLORESCENCE: usually axillary cymes, racemes, or the flowers solitary. FLOWERS: perfect, actinomorphic or zygomorphic; calyx 3-6-lobed, often enlarged and petal-like; corolla absent or reduced to small scales; stamens 5-many, free, or adnate to the style and stigma, forming a gynostemium; pistil 1, 4-6 carpelled; ovary inferior or half-inferior. FRUIT: a capsule. SEEDS: numerous. REFERENCES: Mason, Charles T., Jr. 1999. Aristolochiaceae. Ariz.-Nev. Acad. Sci. 32(1).