1. Plant completely glabrous; seed disc papillose, not tuberculate......................................................................... L. pseudamethystea
- Plant pilose-glandulose, at least on inflorescence; seed disc tuberculate and papillose....................................................................2
2. Seed wing not thickened; calyx lobes subequal.................................................................................................................................3
- Seed wing thickened; calyx lobes unequal, the adaxial longer (L. amethystea aggr.).......................................................................4
3. Pedicels 0.4–3 mm long during flowering, 1.3–4 mm long during fruiting; seed wing 0.12–0.25 mm wide................ L. semialata
- Pedicels 1.5–9 mm long during flowering, 1.5–10 mm long during fruiting; seed wing 0.25–0.5 mm wide..................... L. diffusa
4. Corolla yellow....................................................................................................................................................................................5
- Corolla blue to violet..........................................................................................................................................................................6
5. Inflorescence dense; corolla with violet spots; seeds 1.2–2 × 1–1.8 mm................................... L. amethystea subsp. multipunctata
- Inflorescence loose; corolla without violet spots; seeds 0.9–1.3 × 0.9–1.1 mm............................... L. amethystea subsp. ignescens
6. Stems and leaves mostly glabrous; corolla usually blue to violet.................................................. L. amethystea subsp. amethystea
- Stems and leaves pilose-glandulose; corolla (spur excluded) usually white......................................................................................7
7. Inflorescence up to 1 cm long, dense even during fruiting............................................................... L. amethystea subsp. toloxense
- Inflorescence up to 7.5 cm long, loose to dense during fruiting........................................................................................................8
8. Inflorescence dense during flowering and fruiting; corolla rarely with violet spots in the lower lip; seed tubercles up to 40 µm long........................................................................................................................................................... L. amethystea subsp. aedoi
- Inflorescence often loose in fruiting; corolla with violet spots in the lower lip; seed tubercles up to 60 µm length....................................................................................................................................................................................... L. amethystea subsp. albiflora