Linaria amethystea

Key for the studied taxa (L. amethystea and related species)

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