Thermopsis
Hortus Kew. 3: 3. 1811.
Herbs, perennial, unarmed, usually rhizomatous. Stems erect, ascending, or spreading, glabrate to pubescent. Leaves alternate, odd-pinnate; stipules present, usually persistent, ± foliaceous, dimorphic, proximalmost amplexicaul, scarious, and not blade-bearing, distal ones smaller and narrower, subtending leaves; petiolate; leaflets 3, stipels absent, subpetiolulate, blade margins entire, not glandular-punctate, surfaces glabrous or pubescent. Inflorescences 5–90-flowered, usually terminal, sometimes lateral, racemes; bracts present, deciduous or persistent, apex acute to acuminate; bracteoles absent. Flowers papilionaceous; calyx campanulate, lobes 5, appearing 4-lobed, subequal, abaxial lobes deltate to lanceolate, adaxial lobe double, broader, slightly longer, apex truncate to emarginate; corolla yellow, banner widely ovate, shorter than wing and keel petals, apex usually cleft, sometimes emarginate or short-mucronate, claw cuneate to oblong, replicate to reflexed, wings not adnate to keel, often asymmetric, auriculate, ± length of keel, claw narrowly oblong, keel petals usually asymmetric, auriculate, posteriorly fused, without beak, claw narrowly oblong; stamens 10, distinct, uniform; anthers dorsifixed; ovary short-stipitate, oblong, usually longer than style, pubescent, velutinous, villous, or tomentose [villosulous]; style glabrous; stigma minute. Fruits legumes, persistent, stipitate, stipe 2–4 mm, erect, ascending, or divergent, tan to brown, laterally compressed, straight, arcuate, or, rarely, annular, narrowly elliptic, margins straight, or sinuate or lomentaceous from ovule abortion, papery, not elastic, slowly dehiscent, valves separating from apex through both sutures, sericeous, tomentose, velutinous, villous, glabrate, villosulous, or pubescent. Seeds 1–16, oblong, elliptic, or reniform; often with minute, membranous rim-aril. x = 9.
Distribution
North America, Asia.
Discussion
Species 23 (10 in the flora).
Thermia Nuttall is an illegitimate name that pertains here.
Selected References
None.
Lower Taxa
Key
| 1 | Stipules 0.3–0.8 cm wide, base cuneate, not cordate or clasping. | > 2 |
| 2 | Stems from single, woody rootstock; pedicels glabrate, 7–17 mm, at least as long as bracts; legumes inconspicuously appressed-pubescent; racemes terminal or lateral; plants montane, (300–)700–1600 m. | Thermopsis fraxinifolia |
| 2 | Stems from extensive rhizomes; pedicels villosulous, 4–6 mm, shorter than bracts; legumes densely appressed-pubescent; racemes terminal; plants mostly of piedmont, 300–800 m. | Thermopsis mollis |
| 1 | Stipules 0.5–6 cm wide, base cordate and/or amplexicaul, sometimes acute. | > 3 |
| 3 | Legumes ascending or erect. | > 4 |
| 4 | Leaflet blade surfaces densely pubescent; seeds 1–7(–10); stipules 0.7–6 cm wide. | > 5 |
| 5 | Herbs (2.5–)3–8(–9) dm; stems slender, from rhizomes; racemes 7–30(–35) cm, 10–40-flowered; legumes ascending; widespread in California. | Thermopsis californica |
| 5 | Herbs 12–23 dm; stems thick, from woody rootstock; racemes 25–60 cm, 30–90-flowered; legumes erect; Santa Ynez Mountains, California. | Thermopsis macrophylla |
| 4 | Leaflet blade surfaces sparsely pubescent or glabrous; seeds 6–16; stipules 0.7–2.5 cm wide. | > 6 |
| 6 | Herbs 2–8(–10) dm; stems slender; pedicels 3.5–5 mm; calyx 9–11 mm, lobes 3–5 mm; Rocky Mountains northwest to Washington and Oregon coast, Newfoundland and Quebec. | Thermopsis montana |
| 6 | Herbs 6–18 dm; stems thick; pedicels 2–3 mm; calyx 7–8 mm, lobes 2–3 mm; e, se United States. | Thermopsis villosa |
| 3 | Legumes divergent. | > 7 |
| 7 | Herbs 1.2–3 dm; leaflets 1.7–3.3 × 0.6–2 cm, lateral veins 5–7 pairs; peduncles 1–4 cm; legumes strongly arcuate to annular. | Thermopsis rhombifolia |
| 7 | Herbs 3–18 dm; leaflets 3–11 × (0.5–)2–6.5 cm, lateral veins 6–12 pairs; peduncles 3–10(–11) cm; legumes straight or arcuate. | > 8 |
| 8 | Herbs 8–18 dm; stems thick; leaflet blades 6.5–11 × 2.5–6.5 cm, surfaces tomentose; flowers 1.6–1.8 cm; legumes densely tomentose; Humboldt and Siskiyou counties, California. | Thermopsis robusta |
| 8 | Herbs 3–8(–9) dm; stems slender; leaflet blades 3–7(–8) × 0.5–3.2 cm, surfaces glabrous or glabrate to puberulent; flowers 2–2.9 cm; legumes inconspicuously pubescent; n California to Yamhill County, Oregon, n, e Rocky Mountains, adjacent Great Plains. | > 9 |
| 9 | Branches ascending, weakly to moderately or strongly zigzag; leaflet blades 0.5–2.5 cm wide, apex not emarginate; petioles 1–2.5 cm; legumes usually arcuate or annular, sometimes straight; n, e Rocky Mountains, adjacent Great Plains. | Thermopsis divaricarpa |
| 9 | Branches spreading, moderately to strongly zigzag; leaflet blades 2–3.2 cm wide, apex sometimes emarginate; petioles 2.5–4(–5) cm; legumes straight; n California, w Oregon. | Thermopsis gracilis |