Aristolochia, Linnaeus, 1753

Do, Truong Van, Hoang, Thao Thi, Wen, Fang, Wanke, Stefan, Forbes, Malcolm & Souladeth, Phetlasy, 2023, Aristolochia laotica (subgen. Siphisia), a new species from Northeastern Laos, Phytotaxa 591 (2), pp. 155-163 : 161

Key to the species of Aristolochia from Laos

1. Perianth strongly curved; utricle slightly differentiated; tube U- or horseshoe shaped (in side view); gynostemium 3-lobed ........... ............................................................................................................................................................................. 2 (subgen. Siphisia )

- Perianth straight or slightly curved; utricle well-developed; tube rectilinear or slightly curved (in side view); gynostemium 6- lobed ..............................................................................................................................................................4 (subgen. Aristolochia )

2. Limb cylindric or saccate-shaped …............................................................................................................................... 1. A. laotica

- Limb trumpet-shaped, or discoid or nearly so................................................................................................................................... 3

3. Leaf lamina broadly ovate to cordate. Cymes 3–4-flowered, formed in old woody stems, in clusters of 6–8(–10); limb trumpetshaped… .............................................................................................................................................................. 2. A. faviogonzalezii

- Leaf lamina narrowly elliptic to lanceolate-elliptic. Cymes 1–2-flowered, axillary, solitary or paired; limb discoid or nearly so..... ..................................................................................................................................................................................... 3. A. versicolor

4. Leaves deeply 3-lobed.....................................................................................................................................................4. A. pothieri

- Leaves entire.......................................................................................................................................................................................5

5. Stems zigzag. Petiole less than 0.5 cm long ......................................................................................................... 5. A. harmandiana

- Stems not zigzag. Petiole more than 1 cm long .................................................................................................................................6

6. Leaf base cuneate. Seeds not winged ................................................................................................................................ 6. A. indica

- Leaf base slightly to deeply cordate. Seed winged.............................................................................................................................7

7. Leaf blade broadly ovate, twice as long as broad, glabrous on both sides. Seeds warty on one side ....................... 7. A. acuminata

- Leaf blade narrowly oblong-lanceolate, three-four times longer than broad; puberulous on abaxial leaf surface. Seeds warty on both sides .......................................................................................................................................................................... 8. A. pierrei