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

Published as part of Blanca, Gabriel, Carmona, Rafael, Cueto, Miguel & Fuentes, Julián, 2023, Linaria pseudamethystea (Antirrhineae, Plantaginaceae), a new species mimetic of and apparently sympatric with L. amethystea, pp. 1-18 in Phytotaxa 585 (1) on page 10, DOI: 10.11646/phytotaxa.585.1.1, http://zenodo.org/record/7672858