Plants herbs, shrubs, or climbers. Leaves without stipules; blades alternate, simple, palmately veined. Inflorescences of solitary, clustered, or racemose flowers. Flowers bisexual, radially or bilaterally symmetric; calyces usually petaloid, bases tubular or campanulate with entire or symmetrically 3-lobed limb, or unilateral, or 2-lipped; petals usually absent; stamens usually 6 or more, in 1 or 2 series, filaments short, thick, anthers with 2-thecae, extrose, free ot united with the stule; ovaries inferior, completely or partially 4-6-celled; ovules numerous, in 2 series in each cell;styles united into a column: stigmas 3-many lobed. Fruits capsules, often opening from the base upwards; seeds numerous, with copoius endosperm and minute embryos.
The Angiosperm Phylogeny Group interprets the Aristolochiaceae as including Asaraceae, Hydnoraceae, and Lactoridaceae. OpenHerbarium, by default, follows their family recommendations but occasionally disagrees, as with the APG inclusion of Hydnoraceae and Lactoridaceae in Aristolochiaceae which it treats as separate families. Recognizing the three families is in keeping with tradition, which is based on morphology. Neinhus et al. (2003) published a phylogeny of Aristolochiaceae that included Lactoridaceae but not Hydnoraceae. Based on their results, they recommended continuing to treat Lactoridaceae as a separate family.
This map includes records of Hydnoraceae and Lactoridaceae, taxa OpenHerbarium continues to treat as a distinct family, largely because of the difficulty of preparing a morphological description for the Aristolochiaceae if they are included. Not many records are involved.
