16. Sida regnellii R.E. Fries (1908: 33) (Figures 8, 9A–E, 14O).

Lectotype (designated by Rodrigo 1944: t. 24):— BRAZIL. Rio Grande do Sul. Porto Alegre, Menino Deus, “in campo dumetoso”, 03 March 1902, G. O. A:n Malme (S 13-21620! [digital image]).

Taxonomic notes: — Sida regnellii belongs to section Cordifoliae by the indument densely stellate-tomentose; leaf blades lanceolate to ovate, dentate-crenate throughout, basally more or less cordate, features pointed out by Fryxell (1985) for this section (Table 1). It can be distinguished from similar species by its muticous or submuticous mericarps (with aristae up to 0.5 mm long) and by the pink corolla (Figures 9A–E, 14O).

Distribution, habitat and conservation status: — Sida regnellii occurs in Argentina, Paraguay and Brazil (Minas Gerais, Paraná and Rio Grande do Sul states) (Zuloaga et al. 2008, Bovini 2020). In Rio Grande do Sul the species occurs in Inland sub-montane grassland, Bush grassland, Coastal grassland, Aristida grassland, and in Shallow soil grassland (Figure 8). With the available records, the species is here considered Least Concern (LC) with an EOO of 974,636.157 km ² and an AOO of 304 km ². Although it can be considered EN by the AOO, conditions B(a), B(b) and B(c) were not met. In addition, the species is common in its area of occurrence, mainly in the state of Rio Grande do Sul, which is not reflected in the number of records in herbaria.

Representative specimens: — BRAZIL. Rio Grande do Sul. Bossoroca, Projeto de Assentamento Noel Guarany, 04 April 2009, M . Grings 815 (ICN) ; Caçapava do Sul, beira da BR-153, 26 April 2009, M . Grings 2057 (ICN); Porto Alegre, Glória, 03 February 1950, A . Sehnem 4403 (PACA); Quaraí, Fazenda do Jarau, January 1945, B . Rambo s.n. (PACA 26087); Taquari, Cerro Pelado, 06 December 2000, A . Knob & S. A. L .Bordignon 6620 (UNILASALLE).