Aristolochia L.

Scientific Description

Family Aristolochiaceae.

Habit and leaf form. Shrubs, or lianas, or herbs, or herbaceous climbers; bearing essential oils. Perennial; plants with neither basal nor terminal concentrations of leaves. Climbing, or self supporting (less often); mostly stem twiners. Mesophytic. Leaves alternate; spiral; ‘herbaceous’; petiolate (petiole grooved on upper surface); sheathing to non-sheathing; gland-dotted (pellucid punctate), or not gland-dotted; aromatic; simple. Leaf blades entire, or dissected (then lobed); flat; palmately veined, or pinnately veined; cross-venulate; often cordate. Leaves without stipules; without a persistent basal meristem. Stem anatomy. Nodes tri-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present (2–6 nectary glands at base of utricle). Entomophilous; via diptera. Pollination mechanism conspicuously specialized (via an elaborate system for trapping flies within the perianth tube, involving articulated hairs which subsequently wither to release them).

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in racemes, or in spikes, or in panicles. The terminal inflorescence unit cymose, or racemose. Inflorescences axillary, or cauliflorous. Flowers small to large; malodorous, or odourless; very irregular (usually); cyclic. Perianth sepaline, or of ‘tepals’; 3 (forming a uni- or bilabiate perianth); 1 -whorled; joined. Calyx present (petaloid); 3; when interpreted as such, 1 -whorled; gamosepalous; entire, or lobed. Calyx lobes markedly shorter than the tube. Calyx spreading; valvate (or valvate-induplicate); funnel-shaped, or tubular (straight, curved or S-shaped, inflated near base (utricle) then narrowed into a cylindric or funnel-shaped tube and then expanded into the limb); unequal but not bilabiate, or bilabiate; persistent, or not persistent. Androecium (3–)6, or 12 (? in A. tagala, with 2 stamens below each of the prominent horn-like lobes). Androecial members free of the perianth; united with the gynoecium (forming a gynostemium by fusion to the style of both the filaments and the anthers); coherent (via the (3-)6-lobed gynostemium); 1 - adelphous; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens. Stamens (3–)6, or 12. Anthers cohering; basifixed, or adnate; non-versatile; dehiscing via longitudinal slits; extrorse; tetrasporangiate; appendaged, or unappendaged. Pollen shed as single grains. Gynoecium 6 carpelled. The pistil 6 celled. Carpels isomerous with the perianth to increased in number relative to the perianth. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; inferior. Ovary plurilocular; 6 locular. Epigynous disk present, or absent. Gynoecium stylate. Styles 1, or 6; when more than 1, partially joined; apical. Stigmas dry type, or wet type; papillate; Group II type, or Group III type. Placentation axile. Ovules 20–50 per locule (‘many’); funicled; pendulous, or horizontal; anatropous (or circinotropous ?).

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal (separating along with the upper part of the pedicel into 6 valves). Fruit 6 locular; numerous-seeded. Seeds ovate or triangular; endospermic. Endosperm ruminate, or not ruminate; oily. Seeds winged (often), or wingless. Embryo rudimentary at the time of seed release to weakly differentiated. Testa smooth, or with tubercles. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation not found.