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.

SENNA

Elizabeth McClintock

Perennial, shrub, tree, unarmed or spines weak
Leaves even-1-pinnate, alternate; stipules sometimes small or ephemeral; leaflets 2–10(18) pairs
Inflorescence: raceme or panicle, axillary or terminal
Flower generally slightly bilateral, generally showy; sepals ± free; petals free, generally yellow; stamens free, 7 fertile, 3 sterile, anthers generally > filaments, opening by terminal pores
Fruit dehiscent or not
Seeds few–many
Species in genus: ± 260 species: especially Am tropical, also warm temp, sometimes deserts
Etymology: (Arabic: Sana)
Reference: [Irwin & Barneby 1982 Mem New York Bot Gard 35:1–918]
Some cultivated as orns. Dried leaves of some species cathartic.

Native

S. armata (S. Watson) H.S. Irwin & Barneby

SPINY SENNA

Shrub, armed with weak spines, ± leafless most of year, ± glabrous
Stem 0.5–1 m; branches from base, grooved, ending in a weak thorn or not, green
Leaf: stipules minute or 0; leaflets 2–4 pairs, not overlapped, ± opposite, ephemeral, ± sessile, 4–6 mm, asymmetric, oblong; main axis elongating after leaflets fall, weakly spine-tipped
Inflorescence terminal, raceme-like (flowers 1–2 per axil of upper leaves)
Flower: petals 8–12 mm, obovate, ± irregular, yellow to salmon-red
Fruit dehiscent, 2.5–4 cm, lanceolate, straight
Seeds few
Ecology: Uncommon. Sandy or gravelly washes
Elevation: 200–1000 m.
Bioregional distribution: Desert
Distribution outside California: Nevada, Arizona, Baja California
Flowering time: Mar–Jul
Synonyms: Cassia a. S. Watson
Horticultural information: TRY.