Oxalis sect. Ripariae, Lourteig, 2000

Nuernberg-Silva, Anelise & Fiaschi, Pedro, 2021, Taxonomic revision and morphological delimitation of Oxalis sect. Ripariae (Oxalidaceae), Phytotaxa 529 (1), pp. 125-159 : 132-133

Identification key to species of Oxalis sect. Ripariae

1. Shrubs or erect herb with stem up to ca. 30 cm long; internodes regularly spaced, nodes not rooting; petioles 1–5(9.5) cm long .... ...........................................................................................................................................................................................................2.

- Stoloniferous herbs; stem up to ca. 100 cm long; internodes alternating between very short and long, nodes sometimes rooting; petioles (3) 7–28 cm long...................................................................................................................................................................6.

2. Erect herb; leaflet blades membranous, lacking glandular hairs; apex cleft; peduncles 3.5–12.5 cm long, inflorescences 2–13- flowered.................................................................................................................................................................. Oxalis niederleinii

- Decumbent or scandent-cespitose subshrub; leaflet blades chartaceous, with glandular hairs 0.5–1.5 mm long; apex cleft, obcordate, retuse or rounded, sometimes mucronulate; peduncles 0.5–6(8) cm long, inflorescences 2–5-flowered.........................................3.

3. Hairs up to ca. 2 mm long, thick, yellowish; leaflets apex retuse to obcordate ....................................................... Oxalis eriocarpa

- Hairs up to ca. 1 mm long, thin, transparent; leaflets apex retuse to rounded, sometimes mucronulate or cleft..............................4.

4. Leaflet blades concolorous, widely depressed obtrullate to very widely obtrullate, the apex cleft, margin plane; glandular hairs ca. 1.5 mm long, abundant; capsules 5–6(7–10) × 12–15 mm, locules 3–5-seminate ..................................................... Oxalis refracta

- Leaflet blades discolorous, widely depressed obovate to obovate, the apex retuse to rounded, sometimes mucronulate, margin revolute; glandular hairs 0.5–1 mm long, sparse to occasional; capsules 2.6–4 × 4.7–5.7 mm, locules uniseminate......................5.

5. Scandent-cespitose unbranched subshrub; stem up to ca. 1.8 m long, procumbent; stipules 1.5–3 × 1.2 mm; inflorescences 1–3- flowered, sepals 6.5–10 × 2.5–3 mm ..................................................................................................................... Oxalis paranaensis

- Decumbent branched subshrub; stem up to ca. 0.6 m long, decumbent; stipules ca. 1.1 × 2 mm; inflorescences 2–5-flowered, sepals 4–5.5 × 0.75–1 mm .................................................................................................................................................. Oxalis benjaminii

6. Stem green, nodes slightly radicant; leaflet apex emarginate to obcordate, rarely cleft ...................................................................7.

- Stem reddish, nodes radicant; leaflet apex acute, obtuse, rounded, truncate or retuse .....................................................................8.

7. Leaflet blades 0.8–3.6 × 1–3.1(4.1) cm, the apex emarginate to obcordate, rarely cleft; inflorescences longer than the leaves ........ ....................................................................................................................................................................................... Oxalis riparia

- Leaflet blades 0.8–1.4 × 0.8–1.3 cm, the apex emarginate; inflorescences shorter than the leaves .................... Oxalis lourteigiana

8. Leaflet blades widely rhombic to rhombic, the apex acute, rarely obtuse or rounded; lateral leaflets asymmetric, blade wider part at or below the mid-portion .................................................................................................................................... Oxalis sarmentosa

- Leaflet blades widely depressed obovate to obovate, the apex obtuse, rounded or truncate, sometimes retuse, rarely acute in a few leaflets; lateral leaflets symmetric, blade wider part above the mid-portion ....................................................................................9.

9. Stem glabrous or only with hairs ca. 0.1 mm long, occasional; leaf blades abaxial surface purplish, the apex rounded or truncate.. .................................................................................................................................................................................... Oxalis hepatica

- Stem with smaller hairs ca. 0.1 mm long,moderate to very abundant,longer hairs0.5–1(1.5) mm long, sparse to moderate,and glandular hairs ca. 0.5 mm long, occasional; leaf blades abaxial surface light green or whitish, the apex acute to obtuse or rounded ........10.

10. Leaflet blade abaxial surface with smaller hairs 0.1–0.2 mm long, curved, ascending or patent, abundant, longer hairs 1–2 mm long, appressed, moderate to abundant, the secondary veins visible ............................................................................ Oxalis bifrons

- Leaflet blade abaxial surface with hairs 1–2 mm long, appressed, very abundant, entirely covering the blade, rarely abundant, the secondary veins hidden under the indumentum ....................................................................................................... Oxalis pampeana