Key to the genera and species of Cardiopteridaceae in the flora of Vietnam

Distinction of genera is based on Schori (2016); key to the species of Cardiopteris follows Gagnepain (1911).

1. Liana with whitish latex; leaf blade entire or lobed, truncate to cordate at base, palmatinerved; corolla gamopetalous; stamens epipetalous; fruit a samara with a fleshy terminal appendage....................................................................................2 ( Cardiopteris)

- Trees or shrubs without latex; leaf blade entire, acute to obtuse at base (never cordate), penninerved; corolla choripetalous or gamopetalous; stamens free or epipetalous; fruit a drupe ..................................................................................................................3

2. Inflorescence with 2–6 cincinni; fruit stipe not or shortly exceeding calyx, ca. 2 mm long; fruit distinctly longer than wide, obcordate .................................................................................................................................................... Cardiopteris quinqueloba

- Inflorescence with 15 or more cincinni; fruit stipe greatly exceeding calyx, 7–8 mm long; fruit oval to nearly circular in outline... ....................................................................................................................................................................... Cardiopteris platycarpa

3. Flowers unisexual; corolla gamopetalous, tube often longer than lobes; stamens epipetalous, included in corolla............................ ............................................................................................................................................................... Gonocaryum ( G. lobbianum)

- Flowers bisexual or unisexual; corolla choripetalous; stamens free, exserted from corolla (in female flowers, staminodes included) .................................................................................................................................................... Citronella ( C. suaveolens)