Identification key for Sida sect. Cordifoliae from Bahia, Brazil

1. Leaves narrowly linear, 2.1–3.1 mm wide ............................................................................................. Sida angustissima A.St.-Hil.

- Leaves ovate, elliptic, oblong, or orbicular, 4–60 mm wide ..............................................................................................................2

2. Leaf blades velutinous to villous on the adaxial surface, bearing stellate trichomes with rays longer than 0.5 mm; glandular trichomes rarely present .....................................................................................................................................................................3

- Leaf blades pubescent, puberulent or hirsute on the adaxial surface bearing stellate trichomes with rays shorter than 0.5 mm, or with simple and bifurcate trichomes; glandular trichomes often present...........................................................................................5

3. Petioles (1–)1.2–1.8(–2) mm wide; leaf blades 20–82 × 10–62 mm; calyx divided above the middle; mericarps 8–12 with awns 3–5 mm long, exerted beyond the calyx.................................................................................................................. Sida cordifolia L.

- Petioles 0.6–1(–1.2) mm wide; leaf blades 10–60 × 5–30 mm; calyx lobes divided below or at the middle; mericarps 7–10 with awns ≤ 3 mm, included within the calyx............................................................................................................................................4

4. Stipules ≤ 3 mm long; petioles up to 10 mm; leaves 5-veined with margins denticulate to serrulate; pedicels up to 10 mm ............ ..................................................................................................................................................................... Sida itaparicana Krapov.

- Stipules 5–10 mm long; petioles 10–15 mm; leaves 5–7 veined with margins dentate to serrate (often biserrate); pedicels up to 25 mm ........................................................................................................................................................................ Sida maculata Cav.

5. Shrubs with brachyblasts; stipules ≤ 4.5 mm; leaf blades pubescent or puberulent on the adaxial surface, with stellate and glandular trichomes; terminal inflorescence lax, with long pedicellate flowers, pedicels (8–)9–42(–48) mm long ........................................... .................................................................................................................................................................. Sida brachyclada G.Guerra

- Subshrubs without brachyblasts; stipules ≥ 8 mm; leaf blades hirsute on the adaxial surface, with simple or bifurcate trichomes; terminal inflorescence congested, with short pedicellate flowers, pedicels 2–11 mm long...................... Sida cerradoensis Krapov.