Description: Trees, shrubs or herbs, sometimes climbing or trailing, occasionally spiny.
Leaves alternate or sometimes opposite or whorled, usually compound (variously bipinnate, pinnate or palmate) or simple, sometimes reduced to scales or modified into phyllodes; stipules usually present and sometimes spinose, stipels often present.
Inflorescences racemose or paniculate, sometimes umbellate or cymose or flowers solitary; bracts and bracteoles commonly below flowers, often caducous. Flowers actinomorphic or zygomorphic, usually bisexual, commonly 5-merous. Sepals usually 5, free or more often variously fused into a toothed tube. Petals usually 5, free or sometimes fused, equal or unequal. Stamens commonly 10 or sometimes <10 or numerous, free or variously fused, sometimes reduced to staminodes; anthers 2-locular, opening by longitudinal slits or rarely by pores; uniform or dimorphic. Ovary superior; carpel solitary; ovules usually 2–many, attached to the upper suture; style and stigma terminal.
Fruit usually a pod (legume), mostly dehiscent along both sutures or only along upper suture or sometimes indehiscent or rarely a lomentum [or drupaceous or nut-like]; seeds 1 to many, often with a hard impervious coat, aril often developed but often inconspicuous.
Distribution and occurrence: World: c. 700 genera, 18000 species, widespread, especially tropical to temperate regions. Australia: c. 180 genera, 1900 species, all States.
Angiosperm Phylogeny Website (Family: Fabaceae, Order: Fabales)
The family is of great economic importance for food, timber, forage crops, dyes and horticulturally. Most species have root nodules containing bacteria (Rhizobium species) which are capable of taking up atmospheric nitrogen and converting it into other nitrogenous compounds. Thus many species are capable of growing well in relatively poor soils, and any are commonly grown as fertilizer crops.
Following recent trends this family is accepted with 3 subfamilies (often treated as 3 separate families) distinguished as follows:
| ||Key to the subfamilies|| |
|1||Flowers zygomorphic; petals imbricate, often unequal; stamens 10 or fewer, not forming the conspicuous part of the inflorescence; leaves various, mostly simple or pinnately compound, only occasionally bipinnately compound or reduced to phyllodes.||2|
|Flowers actinomorphic; petals valvate, equal; stamens usually numerous, forming the conspicuous part of the inflorescence; leaves often bipinnately compound or reduced to phyllodes.||Mimosoideae|
|2||Flowers slightly zygomorphic; corolla not papilionaceous, petals ± equal, free, upper petal usually borne internally to the adjacent lateral petals; stamens 10 or fewer, free.||Caesalpinioideae|
|Flowers strongly zygomorphic; corolla papilionaceous, petals not equal, ± united; upper petal (standard) borne externally to the adjacent lateral petals (wings), lower petals ± fused (keel); stamens 10, often united into a tube, or the uppermost filament free, or less commonly all free.|
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