Key to Lindernia s.str. in Madagascar (partly after Fischer 1995)

1. Corolla very small (2–3 mm long), flowers cleistogamic, stamens 2, staminodes minute, present or absent ...................................2

- Corolla much larger (5–14 mm long), cleistogamic flowers absent, stamens 2, staminodes distinct, filiform, always present...... 3

2. Plants prostrate, chasmogamic flowers present, corolla with two filiform staminodes, stigma bilobed ............................................. ................................................................................................................... L. benthami Fischer, Schäferhoff & Müller (2013: 225)

- Plants erect, all flowers cleistogamic, corolla without staminodes, stigma spathulate ....................................................................... ..................................................................... L. madagascariensis (Bonati 1924: 103) Fischer, Schäferhoff & Müller (2013: 226)

3. Plants aquatic, leaves spathulate, obtuse, widest in upper third, on water surface, well developed only in apical part of stem ......... ............................................................................................................................................................. L. natans Fischer (1995: 250)

- Plants terrestrial in humid places, leaves ovate-rounded to lanceolate, acuminate to obtuse, widest at middle, base of stem with well developed leaves ............................................................................................................................................................................... 4

4. Staminodes incurved, falcate, plants minute, resembling a moss, tufted, leaves not exceeding 3 mm of length ................................ .......................................................................................................................................................... L. bryoides Fischer (1995: 248)

- Staminodes straight or only slightly curved, never falcate, leaves generally longer than 3 mm ........ L. rotundifolia - group ..........5

5. Leaves rounded-orbicular to rounded-ovate, leaf length-width ratio 0.8–1.6 ...................................................................................6

- Leaves ovate to lanceolate-ovate, leaf length-width ratio 1.75–3.5 ..................................................................................................8

6. Dense long-stalked glandular hairs on stems, leaves, pedicels and calyx, leaves matt, pedicels 12–20 mm long, corolla 10.5–13 mm long, white with blue spots, free part of staminode 3–3.5 mm, without filiform appendage................................... L. adami-hefiedi

- Short-stalked glandular hairs on pedicel and calyx or only on calyx,, leaves shining, pedicels not exceeding 7 mm of length, corolla not exceeding 10 mm of length, white with blue spots or entirely white, free part of staminode not exceeding 2 mm of length, with or without filiform appendage........................................................................................................................................7

7. Leaves rounded-orbicular, shining, 7–11 × 6–11 mm, pedicel 5–7 mm long, corolla white with blue spots, 8–10 mm long, free part of staminode 2 mm, without filiform appendage ........................................................................................................ L. rotundifolia

- Leaves ovate-orbicular, 4–8 mm × 3–5 mm, pedicel 3–4 mm long, corolla white, sometimes tinged blue but without blue spots, 6 mm long, free part of staminode 1.3 mm long, with filiform appendage 0.1 mm long ...................................................... L. viguieri

8. Plants erect, short-stalked glandular hairs on upper leaves, pedicel and calyx, leaves shining, ovate, 5–7 nm × 2.5–4 mm, acuminate, pedicel 5 mm long, corolla white with blue spots, 5.8–6.2 mm long, free part of staminode 1.2–1.3 mm long, with filiform appendage 0.1 mm long.................................................................................................................................................. L. lemuriana

- Plants prostrate to ascending, glandular hairs absent, leaves lanceolate-ovate, (7) 10–25 mm × (2) 4–8 mm, acuminate to obtuse, pedicel 20–30 mm long, corolla white tinged mauve, 10–12 mm long, free part of staminode 2.5 mm, with filiform appendage 0.3 mm long....................................................................................................................................................................... L. oblongifolia