Oxalis sect. Ripariae Lourteig (2000: 297)

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

Oxalis sect. Ripariae Lourteig (2000: 297) .

Type: Oxalis riparia Norlind (designated by Lourteig 2000: 297).

Description:— Herbs or subshrubs, stem erect, decumbent, scandent or stoloniferous. Stem up to ca. 30 cm, more than 1 m long when stoloniferous; internodes 0.1–12 cm long, hairs in general with two sizes:(0.1–0.5 mm and 0.5–2 mm), straight or curved, glandular hairs at least in the flowers. Stipules connate to the petiole or absent; petioles 0.7–30.5 cm long; pulvina 0.3–2 mm long. Leaf blades 0.4–7.6 × 0.4–4.1 cm, chartaceous or membranous, depressed obovate to obovate, widely rhombic to rhombic, or widely depressed obtrullate to very widely obtrullate, base cuneate, apex retuse, truncate or acute, sometimes mucronulate. Dichasia with 2–13-flowers; peduncle 0.5–18 cm long; bracts lanceolate. Sepals with the base rounded, apex acute; petals 6.5–23 mm long, yellowish, spatulate, the apex crenate-denticulate, adaxially with abundant glandular hairs; shorter stamens glabrous, longer ones with ascending hairs, anthers rimose; pistil with ascending, abundant hairs, stigmas papillose. Capsules 2–7(10) × 3–15 mm, depressed ovoid to ovoid, 5- lobed; seeds 1–3(5) per locule, (1.6) 2.1–3.8 × 1–2.4 mm, ellipsoid, widely ellipsoid or obovoid, rounded at the base, with apex acute; seed surface longitudinally crested, with almost echinate or pustulate projections.

Distribution and habitat: — Oxalis sect. Ripariae is distributed in northern Argentina, extending south to La Pampa and west to Tucumán provinces, southern Paraguay, Uruguay, and southern Brazil, with a single species ( O. riparia ) extending northwards along the Mantiqueira range in southeastern Brazil (fig. 4). Mostly distributed in the Pampa and Atlantic Forest phytogeographic domains, with few collections in the Argentinian Chaco and Piedmont Andean forests, from sea level ( O. pampeana ) to ca. 1,770 m elevation ( O. sarmentosa ). The species preferred habitats are Araucaria forest and trail edges, rural roadsides, grasslands, slopes and river margins. Species richness:— 11 species in the present account ( Table 2 ).