FABACEAE

LEGUME FAMILY

Annual to tree
Leaves generally compound, alternate, stipuled; leaflets generally entire
Inflorescence: generally raceme, spike, umbel or head; flowers sometime 1–2 in axils
Flowers generally bisexual, generally bilateral; hypanthium generally flat or cup-like; sepals generally 5, fused; petals generally 5, free, or the 2 lower ± fused; stamens 1–many, often 10 with 9 filaments at least partly fused, 1 (uppermost) free; pistil 1, ovary superior, generally 1-chambered, ovules 1–many, style, stigma 1
Fruit: legume, sometimes including a stalk-like base above receptacle, dehiscent, or indehiscent and breaking into 1-seeded segments, or indehiscent, 1-seeded, and achene-like
Seeds 1–several, often ± reniform, generally hard, smooth
Genera in family: ± 650 genera, 18,000 species: worldwide; with grasses, requisite in agriculture and most natural ecosystems. Many cultivated, most importantly Arachis , peanut; Glycine , soybean; Phaseolus , beans; Medicago ; Trifolium ; and many orns
Reference: [Polhill & Raven (eds) 1981 Advances in legume systematics; Allen & Allen 1981 Leguminosae]
Family description and key to genera by Duane Isely.

PROSOPIS

MESQUITE

Elizabeth McClintock

Shrub, tree; stipular spines generally 2 per node; roots long, spreading
Leaves even-2-pinnate, alternate, deciduous; 1° leaflets generally 1–2 pairs, opposite; 2° leaflets generally many, opposite
Inflorescence: raceme, axillary, spike-like or spheric head, many-flowered
Flower radial, small, greenish white or yellow; calyx shallowly bell-shaped, lobes very short; petals generally inconspicuous; stamens 10, exserted, free; style exserted, generally appearing before stamens
Fruit indehiscent, ± flat, ± narrowed between seeds or tightly coiled, pulpy when young, then woody
Seeds several
Species in genus: ± 44 species: especially Am (also sw Asia, Africa)
Etymology: (Greek: burdock, for obscure reasons)
Reference: [Burkhart 1976 J Arnold Arbor 57:220–524; Holland 1987 Madroño 34:324–333]
Used for timber, firewood, shade, ornamental, bee, human, and livestock food.

Native

P. pubescens Benth.

SCREW BEAN, TORNILLO

Shrub, tree < 10 m; crown generally ± narrow
Stem: branches ascending; spines 4–12 mm
Leaf hairy; 1° leaflets 1 or 2 pairs, 3–5 cm; 2° leaflets 5–8 pairs, 2–10 mm, oblong, length 2–3 X width
Inflorescence: raceme, 4–8 cm, spike-like
Flower: petals fused, 2–3 mm
Fruit 3–5 cm, tightly coiled
Seeds generally 3 mm, ovoid
Chromosomes: 2n=28
Ecology: Uncommon. Creek, river bottoms, sandy or gravelly washes or ravines
Elevation: 100–1300 m.
Bioregional distribution: San Bernardino Mountains, Desert
Distribution outside California: sw US, n Mexico
Flowering time: Apr–Sep
Fr used for food and as a coffee substitute
Horticultural information: SUN: 7, 14, 15, 16, 18, 19, 20, 21, 22, 23 &IRR: 8, 9, 10, 11, 12, 13; also STBL.