Key to the species of Trigonotis

1Ovary 7-10-lobed, nutlets 7-10
1'Ovary 4-lobed; nutlets 4
2Corolla 7-9 mm in diam. Leaves elliptic- to obovate-oblong, strigose on margin and midrib, otherwise glabrous
2'Corolla c. 4 mm in diam. Leaves orbicular to ovate, conspicuously strigose on both faces
3Leaves linear to linear-lanceolate, acute, not longer than 9 mm.
3'Leaves wider, oblong-obovate to oblanceolate, if linear then much longer than 9mm
4Nutlets angulate dorsally, dorso-ventrally compressed; plants prostrate, flowers solitary above axils of upper leaves
4'Nutlets either angulate dorsally, dorso-ventrally compressed and plants upright in upper part with elongated cymes or nutlets rounded dorsally, or plants prostrate with solitary flowers in axils of upper leaves
5Nutlets angulate dorsally, dorso-ventrally compressed; plants upright in the upper part, with elongated cymes
5'Nutlets rounded dorsally, laterally slightly compressed; plants creeping, prostrate; flowers solitary in the axils of upper leaves
6Bases of lower leaves decurrent, upper leaves stalked
6'Bases of lower leaves rounded or tapering into a petiole
7Leaves strigose along margins only; cymes axillary with 4-6 flowers; stems glabrous
7'Stems and leaves hirsute on whole surface; cymes terminal, often bifurcate, with more numerous flowers
8Ovary and fruit finely hairy; leaves linear to oblong or oblong-lanceolate
8'Ovary and fruit glabrous; leaves oblong to elliptic
9Calyx united for half of its length, lobes ovate-triangular
9'Calyx united for less than half of its length, lobes narrowly ovate to ovate-lanceolate
10Stem densely patent hairy in its lower part, hairs reddish brown when dry. Leaves of flowering stems 0-1, broadest near base, semiamplexicaulous
10'Stem with more or less appressed, antrorse hairs in its whole length, hairs permanently white. All leaves tapering towards base, stalked
11Corolla 4 mm long, tube c. 2 mm; both leaf surfaces densely strigose
11'Corolla 3-9 mm long, tube 2-3(-5) mm; upper leaf surface laxly strigose, hairs sometimes in irregular patches
12Nutlets ciliolate along their margins
12'Nutlets glabrous or minutely papillate
13Plant pulvinate with short stems crowded densely together. Leaves not longer than 8 mm
13'Plant not pulvinate, with elongate, more or less creeping stems. Leaves distinctly longer
14Nutlets minutely papillate, gray or light-brown, dull
14'Nutlets smooth, blackish or black, rarely ivory white, shiny
15Pedicels 0.5-1 mm long. Corolla 3-3.5 mm long, 4.5 mm across
15'Pedicels 8-12 mm long in flower, up to 18 mm in fruit. Corolla 9 mm long, 12 mm across
16Leaves oblanceolate, gradually contracted into the petiole; nutlets lanceolate. Pedicels 2-5 mm long
16'Leaves obovate to elliptic, abruptly contracted into a short, sheathing petiole; nutlets short. Pedicels 1-3 mm in flower, up to 7 mm in fruit.