Apios species

Key to Apios species

With the addition of Apios chindiana described above, the genus now comprises seven species with two varieties. An updated key to species (based on flowering specimens) is provided below.

1. Tubers usually undeveloped; standard flat, fully open when flowering............................................................................... A. carnea View in CoL

-. Roots starchy and tuberous; standard ± hooded, incompletely open when flowering .......................................................................2

2. Corolla asymmetric, upper half of keel twisted to one side ............................................................................................... A. fortunei View in CoL

-. Corolla ± bilaterally symmetric, keel curved at apex but not twisted ................................................................................................3

3. Inflorescence with flowers densely congested towards upper part; wing petals more than half the length of the keel; N America ... ............................................................................................................................................................................................................4

-. Inflorescence with lax flowers; wing petals less than half the length of the keel; China to India.....................................................5

4. Corolla maroon; standard with a short prolongation ( 1.5–2 mm) at the tip .................................................................. A. americana View in CoL

-. Corolla pink; standard with a long prolongation ( 6–8 mm) at the tip ............................................................................... A. priceana View in CoL

5. Leaflets with margins shallowly undulate; corolla reddish to dull green....................................................................... A. chindiana

-. Leaflets entire; corolla white, greenish white, pale yellow, light purple, or dark purple ...................................................................6

6. Terminal leaflet broadly triangular, caudate at apex; wing petals refolded into an S shape; keel curved but not curved to semicircular; plants of C, E & SE China..................................................................................................................................... A. chendezhaoana View in CoL

-. Terminal leaflet ovate, lanceolate to linear, acuminate to acute, or rounded to obtuse at apex; wing petals reflexed but not refolded into an S shape; keel curved to semicircular; plants of SW China to India.......................................................................................7

7. Flowers pale yellow or greenish white, Sichuan and Yunnan, east of the Mekong-Salween Divide........... A. delavayi var. delavayi View in CoL

-. Flowers purple, NE India, Xizang and Yunnan ..................................................................................................................................8

8. Leaflets lanceolate to ovate, apex acute to acuminate; inflorescence 6–30-flowered; Assam ( India), SE Xizang and NW Yunnan ( China), west of the Mekong-Salween Divide .................................... A. delavayi var. pteridietorum Handel-Mazzetti (1933: 580) View in CoL

-. Leaflets linear to narrowly lanceolate, apex acute to rounded or obtuse; inflorescence 2–4-flowered; Central and SE Yunnan ( China).............................................................. A. delavayi var. gracillima ( Dunn 1903: 488) B. Pan bis View in CoL in Zhang et al. (2018: 10)