Aristolochiaceae

1. Stem prostrate, with strong odor of ginger when freshly bruised; leaves in pairs; perianth regular, the tube very short, neither curved nor inflated but cup-shaped; stamens 12, with short filaments inserted on the ovary.

Asarum

1. Stem erect (herbaceous or a woody vine), with odor none or not ginger-like; leaves alternate; perianth bilaterally symmetrical, with elongate and inflated calyx tube; stamens 6, the anthers sessile and adnate to the stigma.

2. Plant a high-twining woody vine with flowers ca. 3 cm or more long; leaves usually more than 8 cm broad.

Isotrema

2. Plant herbaceous, not twining, with flowers less than 3 cm long; leaves (except the largest) less than 8 cm broad.

3. Flowers axillary; perianth ± straight, yellow; principal leaf blades about as broad as long or broader; escaped from cultivation, in ± disturbed places.

Aristolochia

3. Flowers on peduncles arising at the base of the stem; perianth S-shaped, purplish; principal leaf blades distinctly longer than broad; native, in forests.

Endodeca

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. July 26, 2017. http://michiganflora.net/family.aspx?id=Aristolochiaceae.