Flora of North America species comparison

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Acmispon strigosus

Acmispon denticulatus

strigose lotus

meadow birds-foot trefoil, meadow lotus, Mohave trefoil, riverbar bird's-foot-trefoil, riverbar lotus, riverbar trefoil, tooth lotus
Habit Herbs, annual, usually mat-forming, sometimes cespitose (ascending and bushy), green to grayish, 0.3–5 dm, not or ± fleshy, strigillose, hirsute, canescent-tomentose, or scantily pubescent; taprooted. Herbs, annual, cespitose, often glaucous, 0.3–4 dm, not fleshy, glabrous or hirsute; taprooted.
Stems

1–20+, procumbent or decumbent to ascending, branched basally, herbaceous, slender, leafy.

1(–5), decumbent to erect, apically or basally coarse-branched, herbaceous, leafy.
Leaves

irregularly pinnate;

stipules glandlike;

subsessile;

rachis 3–20 mm, flattened;

leaflets 4–10, blades unequal, obovate to oblanceolate to linear-oblong or oblong, apex acute to obtuse or truncate, surfaces ± densely tomentose to glabrate.

subpinnate, pinnate, or palmate;

stipules glandlike or absent; petiolate;

rachis 5–12 mm, flattened;

leaflets 2–4, often 1 or 2 on one side and 2 terminal, blades elliptic to obovate (lateral sometimes asymmetric), margins denticulate or entire, apex acute to obtuse, surfaces hirsute.
Inflorescences

1–3-flowered.

1 or 2-flowered.
Peduncles

ascending or reflexed, upturned, 3–25 mm, shorter to longer than leaves (often elongated in fruit);

bract absent or 1–3-foliolate, usually subtending umbel.

± sessile;

bract absent.
Flowers

(5–)6–10(–12) mm;

calyx 3–5.5 mm, tube ± sparsely strigillose or glabrous, lobes subulate;

corolla yellow (sometimes banner orangish abaxially), turning orange or reddish, claws ± equaling calyx tube, banner implicate-ascending or remaining closely implicate, wings longer than keel;

style corneously thickened, marked by color, straight, puberulent or glabrous.

5–8 mm;

calyx 3–5 mm, tube hirsute or glabrous, lobes subulate, ± denticulate;

corolla cream-white to pale yellow, banner purple-tinged, keel tip yellowish, claws shorter to slightly longer than calyx tube, banner ascending, wings ± equaling keel, with deep, triangular auricle;

style curved, glabrous.
Legumes

persistent, exserted, erect or divergent, brown, straight to ± curved distally, compressed, not or slightly constricted, incompletely septate, linear-oblong, 10–35 × 2–3 mm, thinly leathery, apex initially short-beaked, dehiscent, smooth, margins smooth, thin, glabrous or ± strigose.

persistent, solitary or paired, exserted, erect or spreading, tawny, straight, compressed, slightly constricted, not septate, widely oblong, 8–20 × 3 mm, leathery, apex abruptly downward angled and curved, dehiscent, smooth, margins often undulate-verrucose, strigose or glabrous.
Seeds

5–10, greenish to brown, ± mottled, ovoid to cuboid or globose, rugulose or granular.

(2 or)3(or 4), gray, faintly mottled, asymmetrically ± angular-obovoid, flattened, smooth.
2n

= 12.

Acmispon strigosus

Acmispon denticulatus
Phenology Flowering spring–summer.
Habitat Grassy slopes, meadows, prairies, clearings, gravel bars, stream banks, vernal pools, pastures, grainfields, usually sandy soils, sometimes alkali, clay, or serpentine soils, roadsides.
Elevation 0–1900 m. (0–6200 ft.)
Distribution
sw United States; n Mexico
[BONAP county map]
from FNA
CA; ID; OR; UT; WA; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 3 (3 in the flora).

D. Isely (1981) discussed the variation in Acmispon strigosus (as Lotus), distinguishing three varieties, two rather distinct but with intergrading phases, and one apparently more transitional, although distinct enough to be recognized. These varieties were only noted for California in recent treatments (for example, L. Brouillet 2012, following D. Isely 1993). Nonetheless, the typical (for example, excluding intergrading phases) varieties represent recognizable morphologies that also have geographic distinction. Specimens representing intergradation seem to occur throughout the range of overlap of these varieties, sometimes rendering determination difficult.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Acmispon denticulatus occurs in California from the San Francisco Bay area, Sacramento Valley, and northern Sierra Nevada Foothills to the northwest, Cascade Range and Modoc Plateau, into adjacent southern Oregon (Siskiyou and Klamath regions), northward on both sides of the Cascade Range into southern British Columbia, with eastern outliers in southwestern Utah (Washington County), and in south-central Idaho (Lincoln County).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Herbs evidently hirsute, especially at apex, greenish.
var. hirtellus
1. Herbs usually strigillose or canescent-tomentose to scantly pubescent, rarely strigillose, green or cinereous.
→ 2
2. Stems ascending or decumbent, not markedly succulent, usually appearing green, sometimes cinereous; leaflet blades linear-oblong, apices acute to obtuse; corolla opening; California.
var. strigosus
2. Stems prostrate, succulent, cinereous(–greenish); leaflet blades oblong, apices obtuse or truncate; corolla not opening; Arizona, California, Nevada.
var. tomentellus
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Acmispon Fabaceae > subfam. Faboideae > Acmispon
Sibling taxa
A. americanus, A. argophyllus, A. argyraeus, A. brachycarpus, A. cytisoides, A. decumbens, A. dendroideus, A. denticulatus, A. glaber, A. grandiflorus, A. haydonii, A. intricatus, A. junceus, A. maritimus, A. mearnsii, A. micranthus, A. neomexicanus, A. parviflorus, A. plebeius, A. procumbens, A. prostratus, A. rigidus, A. rubriflorus, A. tomentosus, A. utahensis, A. wrangelianus, A. wrightii
A. americanus, A. argophyllus, A. argyraeus, A. brachycarpus, A. cytisoides, A. decumbens, A. dendroideus, A. glaber, A. grandiflorus, A. haydonii, A. intricatus, A. junceus, A. maritimus, A. mearnsii, A. micranthus, A. neomexicanus, A. parviflorus, A. plebeius, A. procumbens, A. prostratus, A. rigidus, A. rubriflorus, A. strigosus, A. tomentosus, A. utahensis, A. wrangelianus, A. wrightii
Subordinate taxa
A. strigosus var. hirtellus, A. strigosus var. strigosus, A. strigosus var. tomentellus
Synonyms Hosackia strigosa, Anisolotus strigosus, Lotus strigosus, Ottleya strigosa Hosackia denticulata, Anisolotus denticulatus, Lotus denticulatus
Name authority (Nuttall) Brouillet: J. Bot. Res. Inst. Texas 2: 392. (2008) (Drew) D. D. Sokoloff: Ann. Bot. Fenn. 37: 130. (2000)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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