17. Sida rhombifolia Linnaeus (1753: 684) (Figures 9F–J, 10, 14P).

Lectotype designated by Rodrigo 1944: t. 28):— “Habitat in India utraque, rhombifolia. 2”, s.d., s.c., s.n. (LINN 866.3! [digital image], isolectotype S).

Taxonomic notes: —The species can be distinguished from others in section Sidae (Table 1) Series Sida by its stellate-puberulous or farinaceous indumentum, presence of 8–14 mericarps with two awns 2 mm long and without a basal prominence, bracts absent in the flowers, calyx puberulous without long simple trichomes, adaxial surface of leaves subglabrous only with sparse and small stellate trichomes (Figures 9F–J, 14P) (Krapovickas 2014, Yoshikawa et al. 2019). Although Krapovickas (2014) stated that the petals of Sida rhombifolia do not have a red basal spot, individuals with this feature were observed in Rio Grande do Sul.

Distribution, habitat and conservation status: — Sida rhombifolia is a pantropical species almost cosmopolitan (Krapovickas 2014, Brandão et al. 2017), extending into temperate zones (Fryxell 1988, Brandão et al. 2017). In Rio Grande do Sul the species is also widely distributed, occurring in all regions (Figure 10), in ruderal environments and anthropized grasslands. For these reasons, the species is here considered Least Concern (LC).

Representative specimens: — BRAZIL. Rio Grande do Sul. Bagé, rio próximo à cidade, 04 April 1975, B. Irgang et al. s.n. (ICN 027419); Caçapava do Sul, margem da BR-153, 26 April 2009, M. Grings 2058 (ICN); Caxias do Sul, Bairro Nossa Senhora da Saúde, 12 April 2011, J. Gaio 21 (HUCS); Fontoura Xavier, 696 m, WGS 84 28°55’12.5”S 052°21’28.2”W, 02 March 2019, M. Grings 2023 (ICN); Iraí, Balneário Osvaldo Cruz, 24 January 1990, A. Krapovickas & C. L. Cristóbal 43499 (CTES, HAS); Júlio de Castilhos, na BR-392 estrada para Cruz Alta, 28 April 1988, N. Silveira et al.7228 (HAS, ICN); Quaraí, Garopá, 14 January 1941, B. Rambo s.n. (PACA 4175); Rio Grande, Estação Ecológica do Taim, March 1981, J. L. Waechter 1831 (HAS); Santa Maria, Distrito de Santo Antão, Pedra do Lagarto, 230 m, WGS 84 29°37’38.52”S 53°52’25.40”W, 26 December 2018, M. Grings et al. 2005 (ICN); Uruguaiana, Campus Universitário da Unipampa, BR 472, Km 585, 15 April 2011, H. S da Rosa s.n. (ICN 167493); Vacaria, Parque de Rodeios, 27 April 2019, M. Grings 2031 (ICN).