| 1 | Leaves along a distinct, supraterranean, creeping to erect stem. No bulbs. |
| 1' | Stemless herbs with bulbs or subterranean rhizomes; leaves all basal. |
| 2 | Shrublet. Petioles phyllodial, leaflets 0-3, often minute. Peduncles abortive. Flowers 1-9 in a fascicle, yellow. Cultivated in Java (§ Heterophyllum) (O. rusciformis MIKAN). |
| 2' | Herbaceous. Petioles not phyllodial, leaflets not reduced. Peduncle distinct. |
| 3 | Leaf pinnately 3-foliolate (rachis developed under terminal leaflet). Leaflets elliptic to oblong, apex not notched. Petals pink with yellow base (§ Thamnoxys). |
| 3' | Leaf digitately 3-foliolate. Leaflets obcordate. Petals yellow (§ Corniculatae). |
| 4 | Rhizome, no bulbs. Inflorescence 1-flowered. Sepals with 0-1 greenish, round apical callus. Petals white (§ Acetosellae). |
| 4' | Bulbs, no rhizome. Inflorescence 2-many-flowered. Sepals with 2-4 orange apical calli. Petals red or purple with greenish to yellowish base. |
| 5 | Stipules conspicuous, much wider than the petiole. Leaflets up to 1¼ by 1¼ cm, obcordate; beneath whitish and glaucous and with a pale callus in the notch. Bracteoles 2, free, not vaginate, subglabrous. Sepals pubescent, with 1 pale apical callus. |
| 5' | Stipules narrow, slightly broader than petiole, not very conspicuous. Leaflets 1-3 by 1¼-4 cm, fishtail-shaped; beneath not whitish and glaucous, ecallose. Bracteole 1, emarginate to bifid, vaginate, with an apical brown hair-tuft. Sepals subglabrous, ecallose. |
| 6 | Outer tunics many-nerved, fibrous-withering. Leaflets 4(-6), obdeltoid, not notched, not punctate, at apex sometimes with 2 minute calli. Umbel with many bracts. Filaments crispy-ciliate, the longer with a dorsal tooth. Sepals with 4 linear calli. Petals red (bluish when dry) (§ Polyoxalis). |
| 6' | Outer tunics 3-several-nerved, not fibrous. Leaflets 3, obcordate or fishtail-shaped. Sepals with 2 oblong apical calli. Petals purple (bluish when dry) (§ Jonoxalis). |
| 7 | Stolons apically bulbiferous. Outer tunics membranaceous, transparent, several-nerved. Leaflets fishtail-shaped, not punctate, notch often with 2 minute calli. Bracts of umbellate inflorescence 2, opposite. All filaments moderately ciliate, the longer with a minute tooth. |
| 7' | Stolons absent, bulb consisting of many small bulbils; outer tunics papyraceous, brownish, 3-nerved. Leaflets broadly obcordate, minutely punctate all over the surface, especially along the margins, ecallose. Bracts of the cymose, contracted inflorescence many. Shorter filaments glabrous, the longer ciliate, without a tooth. |
