| | 1. Inflorescence of lateral clusters on 1 side of axis |
| |
| | 2. Calyx lobes long-tapered, hairy; corolla generally white to lavender, tube 25–45 mm |
| I. tenuituba |
| | 2' Calyx lobes deltate to acuminate, sparsely hairy; corolla generally red, tube 10–30 mm |
| |
| | 3. Corolla tube 10–20 mm; anthers included in tube; Desert Mountains |
| I. arizonica |
| | 3' Corolla tube 20–30 mm; anthers included in throat or exserted; widespread |
| I. aggregata |
| | 4. Pollen blue; cauline leaf lobes blunt to rounded |
| subsp. bridgesii |
| | 4' Pollen generally white or yellow; cauline leaf lobes acute |
| subsp. formosissima |
| | 1' Inflorescence not 1-sided; terminal, open, and few-flowered, or head-like and bracted, or flowers solitary in lower axils |
| |
| I. tenuifolia |
| | 5' Corolla generally < 10 mm, white to deep pink |
| |
| I. congesta |
| subsp. congesta |
| |
| | 8. Leaf lobes generally 3; stem < 1 dm; alpine |
| subsp. montana |
| | 8' Leaf lobes generally 5; stem 1–3 dm; montane |
| subsp. palmifrons |
| |
| | 9. Corolla deep pink or white mottled with pink; stamens exserted |
| I. effusa |
| | 9' Corolla generally white; stamens generally including |
| |
| | 10. Leaves entire to slightly toothed, linear to elliptic; lower flowers 1–3 in axil |
| I. depressa |
| | 10' Leaves generally pinnately lobed, generally oblanceolate; flowers terminal |
| I. polycladon
|