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scurfpea, subterranean Indian breadroot

Chihuahua scurfpea, small Indian breadroot

Habit Herbs usually acaulescent, rarely subacaulescent, to 25 cm, pubescent throughout and eglandular or sparsely glandular with pale, sunken obscure glands on leaflets and/or calyx tubes only. Herbs subacaulescent, to 30 cm, mostly glandular (with obvious blond to dark brown glands) and appressed-spreading pubescent throughout.
Stems

short-erect, with decumbent laterals, decumbent stems 0–6 cm, overtopped by leaves, leaves clustered;

pseudoscapes usually 1, unbranched, rarely 2, 0.5–9.5 cm;

cataphylls 5–20 mm.

mostly very short-erect, sparsely branched, with leaves clustered at base, rarely with decumbent lateral stems 0–15 cm, with leaves and inflorescences in terminal clusters;

pseudoscapes 0–4 cm;

cataphylls 7–15 mm (when present), apically emarginate.

Leaves

palmately (3–)5-foliolate;

stipules persistent, linear-lanceolate to elliptic, 4–19 × 2–6 mm, appressed-pubescent;

petiole not obviously jointed basally, (20–)30–210 mm;

petiolules 1–3 mm;

leaflet blades elliptic to lanceolate, oblanceolate, or rhombic, 1–7.5 × 0.3–4 cm, base cuneate, apex acuminate, surfaces glabrate to sparsely pubescent.

palmately or pseudopalmately 5(or 6)-foliolate, sometimes with 2 leaflets distal to others;

stipules persistent, lanceolate to linear, 9–15 × 5 mm, strigose-tomentose;

petiole jointed basally, 60–150 mm, strigose-tomentose;

petiolules 1.5–2 mm;

leaflet blades lanceolate, rhombic, or slightly oblanceolate, 2–5.5 × (1.5–)2–3.2 cm, base cuneate, margins undulate, apex acute, mucronate, surfaces glandular and pubescent.

Inflorescences

disjointing in age at peduncle base, ovate to oblong;

rachis 0.5–6 cm, elongating slightly in fruit, nodes 3–15, 3 flowers per node, internodes crowded in flower, elongating to 25 mm in fruit;

bracts mostly persistent or very tardily deciduous, linear to oblanceolate or rhombic, 3–11 × 1.5–4.5 mm, appressed-pubescent.

disjointing in age at peduncle base, globose to long-ovoid;

rachis 2–4.5 cm, nodes 6–9, 3 flowers per node;

bracts persistent to tardily deciduous, lanceolate to elliptic, often ensiform, 5–7 × 2–3 mm, membranous in age, strigose.

Peduncles

1–14 cm, shorter than subtending petiole, subappressed-pubescent.

(3–)4–9.5 cm, equal to or shorter than subtending petiole, appressed-pubescent.

Pedicels

1–5 mm.

2–3 mm.

Flowers

11–18 mm;

calyx weakly gibbous-campanulate in fruit, 9–15 mm abaxially, 6–14 mm adaxially, usually eglandular, very rarely glandular on tube, pubescent;

tube 2.5–6 mm;

lobes subulate or linear-lanceolate to lanceolate, abaxial 6–10 × 1.5–3(–4) mm, adaxial 4.5–9 × 1–1.5 mm;

corolla lavender to purple, banner paler, sometimes also marginally white, elliptic to obovate, 11–18 × 4–7 mm with claw 2–5 mm, wings 11–16 × 2–3 mm with claw 3.5–6 mm, keel 6–12 × 2–3 mm with claw 2.5–7 mm;

filaments 6–11 mm;

anthers round to elliptic, 0.3–0.5 mm;

ovary glabrous or pubescent apically, style pubescent basally.

14–18 mm;

calyx gibbous-campanulate in fruit, 14–16 mm abaxially, 11–12 mm adaxially, glandular, strigose;

tube 4–5 mm;

abaxial lobe broadly oblanceolate, 10–12 × 3.5–4 mm, adaxial lobes linear-lanceolate, 7–8 × 1–1.5 mm;

corolla white to purple, banner white to lavender, paler than other petals, lanceolate to elliptic, 15–17 × 6–7 mm with claw 4–5 mm, wings 15–16 × 3–3.5 mm with claw 6 mm, keel 9–12 × 3 mm with claw 6–7 mm;

filaments 8.5–10.5 mm;

anthers round-elliptic, 0.3 mm;

ovary pubescent apically, style pubescent basally.

Legumes

ellipsoid-lanceoloid to oblong, 5–6.5 × 3–5 mm, eglandular, glabrous or slightly pubescent, beak 7–19 mm, exserted beyond calyx.

ellipsoid-oblanceoloid, 7–8 × 4–5 mm, eglandular, pubescent, beak broad, flat, 10–15 mm, barely exserted beyond calyx.

Seed

red-brown or gray, globose-reniform, 4–5 × 2.5–3.5 mm, smooth to somewhat rugose.

gray-green to brown, oblong-reniform, 5–6 × 3–4 mm, rugose.

2n

= 22.

Pediomelum hypogaeum

Pediomelum pentaphyllum

Phenology Flowering spring–early summer.
Habitat Desert grasslands.
Elevation 1500–2000 m. (4900–6600 ft.)
Distribution
from USDA
w United States; c United States
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; NM; TX; Mexico (Chihuahua)
[BONAP county map]
Discussion

Varieties 3 (3 in the flora).

J. W. Grimes (1990) recognized three varieties under Pediomelum hypogaeum. Many specimens exist with intermediate traits that obscure strong delineations between taxa.

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

A history of the confusing nomenclature of Pediomelum pentaphyllum was given by P. Tonne (2000). The name was misapplied by P. A. Rydberg (1919–1920); the plant that Rydberg described as P. pentaphyllum was actually P. palmeri; the plant denoted here as P. pentaphyllum was called P. trinervatum Rydberg. J. W. Grimes (1990), before completion of his monograph, erroneously annotated several P. pentaphyllum specimens as P. trinervatum.

Pediomelum pentaphyllum is rare, with only a few confirmed populations in Arizona (Cochise and Graham counties) and New Mexico (Hidalgo County); it was also collected in Texas (Presidio County), and Chihuahua, Mexico (P. Tonne 2000), but may be extirpated in those states.

Pediomelum pentaphyllum is said to have been used by Native Americans and indigenous Mexicans as a fever reducer, the use of which may have contributed historically to its spread through cultivation. It is uncertain as to why P. pentaphyllum has declined, but causes may include over-collecting, grazing, and herbicide application (WildEarth Guardians, https://pdf.wildearthguardians.org/site/DocServer/petition_scurfpea.pdf?docID=624&AddInterest=1103).

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

Key
1. Peduncles 1–3.5 cm, less than 1/2 as long as sub­tending petiole.
var. hypogaeum
1. Peduncles (1.7–)4–14 cm, more than 1/2 as long as subtending petiole.
→ 2
2. Peduncles appressed-pubescent; leaflet blades lanceolate to elliptic.
var. scaposum
2. Peduncles hirsute-villous; leaflet blades oblan­ceolate to rhombic.
var. subulatum
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Pediomelum Fabaceae > subfam. Faboideae > Pediomelum
Sibling taxa
P. argophyllum, P. aromaticum, P. californicum, P. canescens, P. castoreum, P. cuspidatum, P. cyphocalyx, P. digitatum, P. epipsilum, P. esculentum, P. humile, P. latestipulatum, P. linearifolium, P. megalanthum, P. mephiticum, P. palmeri, P. pariense, P. pentaphyllum, P. piedmontanum, P. reverchonii, P. rhombifolium, P. subacaule, P. tenuiflorum, P. verdiense
P. argophyllum, P. aromaticum, P. californicum, P. canescens, P. castoreum, P. cuspidatum, P. cyphocalyx, P. digitatum, P. epipsilum, P. esculentum, P. humile, P. hypogaeum, P. latestipulatum, P. linearifolium, P. megalanthum, P. mephiticum, P. palmeri, P. pariense, P. piedmontanum, P. reverchonii, P. rhombifolium, P. subacaule, P. tenuiflorum, P. verdiense
Subordinate taxa
P. hypogaeum var. hypogaeum, P. hypogaeum var. scaposum, P. hypogaeum var. subulatum
Synonyms Psoralea hypogaea Psoralea pentaphylla
Name authority (Nuttall) Rydberg in N. L. Britton et al.: N. Amer. Fl. 24: 21. (1919) (Linnaeus) Rydberg in N. L. Britton et al.: N. Amer. Fl. 24: 23. (1919)
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