Herbs, annual or perennial, shrubs or subshrubs, unarmed. Stems procumbent or decumbent to ascending or erect, glabrous or pubescent. Leaves alternate, odd- or even-pinnate, palmate, or subpalmate; stipules usually present, glandlike, ovate, or conic, sometimes absent; sessile, subsessile, or petiolate; leaflets (2 or)3–10(–12), blade margins usually entire (sometimes denticulate in A. americanus, A. denticulatus), surfaces usually pubescent, rarely glabrous. Inflorescences solitary flowers or 2–12(–20)-flowered umbels, axillary; bracts present, usually subtending umbel or distal on pedicel, or absent. Flowers papilionaceous; calyx symmetric, bell-shaped or short-cylindric, lobes 5; corolla yellow to orange-yellow, cream, greenish white, white, pink, salmon, or pinkish red, sometimes marked with red, turning pink, orange, red, or brown, banner equaling or shorter than wings, wings symmetric or asymmetric, one wing ± above and one under keel; stamens 10, diadelphous; anthers basifixed, longitudinal; style with or without collar; stigma terminal. Fruits legumes, persistent or deciduous at base of pedicel with persistent calyx, included to ± strongly exserted from calyx, sessile, straight or ± curved to arched at apex, deflexed or not, usually linear to oblong or ovoid, rarely lanceoloid, abruptly short-beaked or tapered into an incurved beak exserted from calyx and appearing hooked, dehiscent or indehiscent, glabrous, glabrate, or ± strigillose to villous or silky. Seeds 1–10(–30), mottled or not, oblong, obovoid, ovoid, elliptic, lenticular, globose, subglobose, reniform, or cylindric. x = 6, 7.

Distribution

North America, nw Mexico, South America (Chile).

Discussion

Species 34 (28 in the flora).

Six species of Acmispon are found only in Mexico [A. flexuosus (Greene) Brouillet, A. niveus (S. Watson) Brouillet, A. nudatus (Greene) Brouillet, A. oroboides (Kunth) Brouillet, A. watsonii (Vasey & Rose) Brouillet] or in Chile [A. subpinnatus (Lagasca) D. D. Sokoloff].

Throughout the twentieth century, Acmispon was usually included within Lotus (D. Isely 1981, 1993). Recent phylogenetic work, both morphologic (A. M. Arambarri 2000) and molecular (G. J. Allan and J. M. Porter 2000; Allan et al. 2003; D. D. Sokoloff et al. 2007), has shown that Acmispon is distinct from the Eurasian Lotus and the North American Hosackia. Notable differences among the three genera include the leafy or scarious, caducous stipules in Hosackia (where leaves are odd-pinnate) versus glandlike in Lotus (leaves with a pair of basal leaflets in stipular position with three palmate terminal leaflets) and Acmispon (leaves odd- or even-pinnate, palmate, or subpalmate).

In Acmispon and Hosackia, the banner sometimes is implicate, remaining folded longitudi­nally and enclosing the rest of the petals; if the banner is implicate-ascending, it remains folded but is partially raised above the other petals.

Selected References

None.

Lower Taxa

Acmispon americanus, Acmispon argophyllus, Acmispon argyraeus, Acmispon brachycarpus, Acmispon cytisoides, Acmispon decumbens, Acmispon dendroideus, Acmispon denticulatus, Acmispon glaber, Acmispon grandiflorus, Acmispon haydonii, Acmispon intricatus, Acmispon junceus, Acmispon maritimus, Acmispon mearnsii, Acmispon micranthus, Acmispon neomexicanus, Acmispon parviflorus, Acmispon plebeius, Acmispon procumbens, Acmispon prostratus, Acmispon rigidus, Acmispon rubriflorus, Acmispon strigosus, Acmispon tomentosus, Acmispon utahensis, Acmispon wrangelianus, Acmispon wrightii

Key

1	Shrubs or subshrubs (sometimes perennial herbs in A. procumbens), usually bushy or erect to procumbent, rarely mat-forming, prostrate, or cespitose.	> 2
2	Leaves usually subpalmate (sometimes only distally), sometimes pinnate, leaflets 3 (except A. glaber sometimes to 7); inflorescences 1–3(–7)-flowered.	> 3
3	Herbs perennial, sometimes subshrubs, gray-canescent or strigose; stems leafy; wings longer than keel; seeds 2 or 3+.	Acmispon procumbens
3	Subshrubs, green, strigose, strigillose, or glabrous; stems remotely leafy; wings shorter than or equaling keel; seeds 1 or 2.	> 4
4	Leaf rachises 2–8(–10) mm; leaflet blades elliptic to lanceolate, apex acute; inflorescences (1 or)2–7-flowered; flowers 7–12 mm; petal claws slightly longer than calyx tube; legumes greenish to reddish brown, linear-oblong, curved to ± straight, 10–15 mm, smooth.	Acmispon glaber
4	Leaf rachises absent; leaflet blades elliptic, apex obtuse; inflorescences 1(or 2)-flowered; flowers 4–5 mm; petal claws shorter than calyx tube; legumes tawny, oblong, curved, (5–)6–9 mm, finely veined.	Acmispon haydonii
2	Leaves pinnate (usually irregularly) or subpalmate, leaflets 3–6; inflorescences (1 or)2–12-flowered.	> 5
5	Plants green or gray; stems erect or decumbent, woody; leaflet blades sparsely to densely strigose (and wings ± equaling keel); California Channel Islands.	Acmispon dendroideus
5	Plants green, greenish, or brownish; stems usually procumbent to ± ascending, sometimes erect to spreading (wiry or stout), herbaceous, sometimes ± woody; leaflet blades strigillose or strigose (and wings longer than keel in A. rigidus), to glabrate or glabrous; mainland w United States, nw Mexico.	> 6
6	Leaflet blades strigose; peduncles much longer than leaves, 20–60(–130) mm; legumes dehiscent, straight, short-beaked; seeds 18–30.	Acmispon rigidus
6	Leaflet blades strigillose to glabrate or glabrous; peduncles shorter than leaves, 0–10 mm, or if longer, to 25 mm; legumes indehiscent, usually curved, sometimes straight, beaked to long-beaked; seeds 1 or 2.	> 7
7	Plants often bushy, sometimes mat-forming, robust, 5–20 dm; stems usually erect to spreading, sometimes procumbent, herbaceous, slender, remotely leafy; inflorescences in axil of distal leaves, spaced or congested, peduncles 0–2 mm; legumes curved to ± straight.	Acmispon glaber
7	Plants usually mat-forming, cespitose, or prostrate, sometimes bushy or wiry, 0.8–8 dm; stems procumbent to ascending, wiry, thick or stout, leafy; inflorescence peduncles 1–25 mm; legumes arched.	> 8
8	Stems greenish; flowers 8–10 mm; petal claws shorter than calyx tube, wings slightly longer than keel; legumes mostly included.	Acmispon cytisoides
8	Stems brownish; flowers 6–8 mm; petal claws longer than calyx tube, wings shorter than keel (and other petals); legumes ± exserted.	Acmispon junceus
1	Herbs annual or perennial (rarely subshrubs), mat-forming, cespitose, or prostrate.	> 9
9	Herbs annual, cespitose, sometimes mat-forming or solitary; taprooted.	> 10
10	Inflorescences 2–8-flowered; legumes indehiscent, strongly exserted from calyx, arched, turgid, constricted between seeds; seeds 2, mottled.	> 11
11	Stems remotely leafy; inflorescences 3–8-flowered, peduncles 8–30 mm; flowers 5–7 mm, claws longer than calyx tube, wings equaling or longer than keel; legumes glabrous.	Acmispon prostratus
11	Stems leafy; inflorescences 2–5-flowered, peduncles 1–2(–5) mm; flowers 3–4(–5) mm, claws shorter than calyx tube, wings shorter than keel; legumes strigillose.	Acmispon micranthus
10	Inflorescences 1 or 2(–5)-flowered; legumes dehiscent, exserted from calyx (except mostly included in A. rubriflorus), usually straight or ± curved, compressed, not or slightly constricted between seeds; seeds 2–10, not or faintly or ± mottled (often black-mottled in A. americanus).	> 12
12	Leaves tomentose or tomentulose to glabrate; wings equaling or longer than keel, styles puberulent or glabrous.	> 13
13	Herbs usually mat-forming, sometimes cespitose, strigillose, hirsute, canescent-tomentose, or scantily pubescent; wings longer than keel.	Acmispon strigosus
13	Herbs not mat-forming (rounded, straggly), glabrate; wings equaling keel.	Acmispon intricatus
12	Leaves glabrous, sparsely appressed-hairy, hirsute, or villous to pubescent, strigillose, or strigose; wings ± equaling or shorter than keel; styles glabrous.	> 14
14	Plants usually glabrous or strigillose, sometimes glabrate to ± pilose; inflorescences 1–5-flowered; peduncles (0–)3–25 mm, bracts usually 1–3-foliolate, rarely absent; legumes straight or ± curved; seeds 3–9.	> 15
15	Plants ± fleshy; stems procumbent to ascending; leaves pinnate, leaflets (3–)5–7; inflorescences 1–5-flowered, pedunculate; corollas bright yellow or orange-yellow; legumes leathery.	Acmispon maritimus
15	Plants not fleshy; stems erect to procumbent; leaves pinnate or palmate, leaflets (1–)3–5; inflorescences 1 or 2-flowered, subsessile or pedunculate; corollas pink or salmon, or whitish or cream; legumes thinly leathery.	> 16
16	Leaflet blades obovate to oblong or elliptic, apex obtuse, surfaces strigose; flowers (2.5–)4–6 mm, calyx tube sparsely strigillose, corollas pink or salmon, claws longer than calyx tube; legumes hook-beaked; seeds not mottled.	Acmispon parviflorus
16	Leaflet blades obovate, ovate, or elliptic to lanceolate, apex acute, surfaces sparsely appressed-hairy; flowers (4–)5–9 mm, calyx tube pilose, corollas whitish or cream, claws shorter than calyx tube; legume apex abruptly downward angled and curved; seeds often black-mottled.	Acmispon americanus
14	Plants usually hirsute, villous, or pubescent, sometimes glabrate or glabrous; inflorescences 1 or 2-flowered; peduncles 0–2 mm, bracts absent; legumes straight; seeds 2–4(–7).	> 17
17	Stems decumbent to ascending or erect; leaflet blades hirsute or villous; calyx lobes subulate; corollas cream-white to pale yellow and banner purple-tinged, or bright pinkish red.	> 18
18	Leaves petiolate, rachises 5–12 mm, leaflet blades elliptic to obo­vate; legumes exserted, 8–20 mm, leathery, strigose or glabrous.	Acmispon denticulatus
18	Leaves subsessile, rachises 4–6 mm, leaflet blades lanceolate; legumes mostly included, 8–9 mm, papery, villous.	Acmispon rubriflorus
17	Stems procumbent to low-ascending; leaflet blades villous or pubescent; calyx lobes lanceolate; corollas yellow, or pale yellow and reddish-tipped.	> 19
19	Plants not fleshy; leaves petiolate; wings shorter than keel; legumes thinly leathery, pubescent (to glabrate), ± septate.	Acmispon wrangelianus
19	Plants ± fleshy; leaves subsessile or sessile; wings ± equaling keel; legumes stiffly papery, villous, not septate.	Acmispon brachycarpus
9	Herbs perennial (rarely subshrubs), usually mat-forming, sometimes bushy, from woody caudices, rhizomatous caudices, or woody-taprooted.	> 20
20	Flowers 4–12 mm; styles curved, geniculate 90°, or incurved; legumes indehiscent, strongly arched or curved, sometimes ± straight, apex tapering, short- or long-beaked, beak sometimes curved; leaves subpalmate, sometimes irregularly pinnate.	> 21
21	Leaves subpalmate, leaflets usually 3, blades canescent to strigose; stems gray-canescent or strigose; calyx tube ± densely strigose; petal claws longer than calyx tube, wings longer than keel; seeds 2 or 3+.	Acmispon procumbens
21	Leaves irregularly pinnate or subpalmate, leaflets 3–6(or 7), blades pilose, villous, or densely sericeous; stems tomentose to canescent, strigose, or ± villous (young) to glabrate (mature); calyx tube villous or sparsely or densely villosulous; petal claws shorter than or equaling calyx tube; seeds 1 or 2(or 3).	> 22
22	Leaflet blades sparsely to densely pilose; flowers 4–6(–7) mm, calyx lobes setaceous; legumes 3–5 mm, villous.	Acmispon tomentosus
22	Leaflet blades villous or densely sericeous; flowers 4.5–12 mm, calyx lobes subulate; legumes 6–10 mm, strigillose or glabrate to silky.	> 23
23	Stems ± villous to glabrate; leaflet blades villous; calyx tube sparsely villosulous; corollas: wings longer than keel; legumes exserted, ovoid- ellipsoid, strigillose.	Acmispon decumbens
23	Stems tomentose to canescent or strigose; leaflet blades densely sericeous; calyx tube densely villous; corollas: wings ± equaling keel; legumes included to moderately(–strongly) exserted, lanceoloid, glabrate to silky.	Acmispon argophyllus
20	Flowers 5–25 mm; styles straight or slightly curved, sometimes basally curved; legumes dehiscent, usually straight, ± curved, or curved distally, apex short-beaked; leaves palmate or pinnate, or subpalmate to irregularly pinnate.	> 24
24	Stems stiff; leaves palmate and leaflets villous to strigose.	> 25
25	Leaves sessile; inflorescences (1 or)2–5(or 6)-flowered, peduncles longer than leaves, (10–)20–50(–80) mm, bracts 1–3-foliolate; banners recurved ca. 45°.	Acmispon utahensis
25	Leaves short-petiolate proximally, subsessile or sessile distally; inflorescences 1 or 2-flowered, peduncles usually longer, sometimes shorter, than leaves, 0–30 mm, bracts absent or (when pedunculate) unifoliolate; banners implicate-ascending.	Acmispon wrightii
24	Stems herbaceous; leaves pinnate to subpalmate (distal) and leaflets gray-puberulent, villous, tomentose, strigose, strigillose, or puberulent, or if palmate, then leaflets seri­ceous to canescent.	> 26
26	Leaves pinnate, leaflets 7–9(–12); corollas greenish white, white, or yellow, fading rose or reddish.	Acmispon grandiflorus
26	Leaves pinnate or subpalmate, leaflets 3–5(–7)[–13]; corollas usually yellow or cream to orange-yellow.	> 27
27	Petal claws ± equaling calyx tube; flowers 5–16(–20) mm; legumes straight or ± curved, slightly constricted between seeds.	> 28
28	Plants silvery or gray, sericeous to canescent; rachises 1–4 mm; legumes turgid.	Acmispon argyraeus
28	Plants green, ± strigose to puberulent; rachises (1.5–)5–10 mm; legumes compressed.	Acmispon plebeius
27	Petal claws shorter than calyx tube; flowers (10–)12–22 mm; legumes straight, not constricted between seeds.	> 29
29	Plants greenish, densely hirsute; leaf blades villous to tomentose; inflo­rescences 1–3(–5)-flowered; calyx tubes densely villous; banners obliquely ascending.	Acmispon neomexicanus
29	Plants silvery, tomentose; leaf blades gray-puberulent; inflorescences (1 or)2–7-flowered; calyx tubes puberulent; banners ascending 45–90°.	Acmispon mearnsii