Fabaceae  

Fabaceae (or known as Leguminosae) is a large and economically important family of flowering plants. It is commonly known as the legume family, pea family, bean family or pulse family. The name ‘Fabaceae’ comes from the defunct genus Faba, now included into Vicia. However, Leguminosae is still considered a valid name. Fabaceae is the 3rd largest family of flowering plants, with some 730 genera and over 19,400 species. The largest genus is Astragalus, with more than 2,000 species. Acacia have more than 900 species, Indigofera have some 700 species, Crotalaria have 600 species, and Mimosa have 500 species. The Fabaceae are placed in the order Fabales, according to most taxonomic system.

The Fabaceae comprise 3 subfamilies:Mimosoideae, Caesalpinioideae, and Faboideae/Papilionoideae.

1- Papilionaceae

Trees, shrubs, lianas or erect to scrambling, annual to perennial herbs. Leaves small to large, usually alternate, pulvinate or epulvinate, mostly pinnate or palmate compound or sometimes simple; stipules present or absent, when present intrapetiolar, free or adnate to petiole, scaly, leafy or spiny or reduced to glands, caducous or persistent; leaflets pulvinate or not, opposite or so, entire or serrate, stipellate or exstipellate, sometimes modified to tendrils, spines or cusps. Flowers zygomorphic, rarely ± actinomorphic, minute to large, in terminal, axillary, or leaf-opposed racemes or pseudoracemes, spikes, capitate heads, fascicles and panicles, rarely flowers solitary axillary; bracteate or ebracteate, bracteoles present or absent. Calyx usually 5-merous, sepals basally united into a campanulate or narrow tube, bilabilate or regular, persistent or deciduous, teeth unequal, or subequal. Corolla 5-merous, papilionaceous, white, yellow, orange, red, pink, purple or blue, petals clawed or sessile, free or partially united below, sometimes adnate to the androecial tube, descending imbricate with adaxial petal forming vexillum or standard, deciduous or party persistent. Stamens (5-) 9-10 (-30), filaments equal or markedly unequal, monadelphous or diadelphous (9+1 or 5+5), anthers free or connivent, dorsifixed or alternately dorsifixed and basifixed, versatile or non-verstile, dehiscence logitudinal. Ovary superior, sessile to stipitate, hairy or glabrous, monocarpellary, unilocular or incompletely to rarely completely bilocular, ovules (1-) 2-100, anatropous or campylotropus to amphitropous; style mostly incurved, glabrous or variously hairy, with capitate or oblique stigma. Fruit an elastically or passively dehiscent legume or hard and indehiscent pod or a lomentum splitting between the seeds, dry or fleshy. Seeds exalbuminous or with scanty endosperm, usually estrophiolate, sometimes arillate.

An economically important large family comprising nearly 500 genera and about 12,000 species, distributed all over the globe. Represented in Saudi Arabia by 46 genera.

2- Caesalpiniaceae

Herbs, shrub and trees, sometimes woody climbers, unarmed or armed. Leaves alternate, stipulate exstipulate, 1 - 2- pinnate, rarely simple. Flowers bisexual, rarely unisexual, hypogynous, more or less zygomorphic, arranged in axillary or terminal racemes, or cymose or spicate to umbellate. Sepal 5, free, imbricate or partly united. Petals 5 or fewer or sometimes missing; imbricate with the posterior innermost. Stamens 10 or fewer, rarely numerous, free or variously connate. Ovary 1-carpellary, 1-celled, superior, sessile or stipitate. Fruit a dehiscent or indehiscent pod, sometimes lomentaceous, rarely winged samara-like. It includes about 150 genera of which 4 are represented in nature in Saudi Arabia while Caesalpinia L. and Parkinsonia L. are often seen as cultivated ornamentals.

3- Mimosaceae

Herbs, shrubs or trees, often spiny. Leaves compound. Flowers small, actinomorphic, 5-merous, borne in globular heads or spikes or spicate racemes. Calyx gamosepalous, 5-dentate. Corolla of 5 free or united petals. Stamens 10 or numerous with the filaments free from each other or monadelphous near the base. Ovary monocarpellary with 1-many ovules on marginal placentation. Fruit dehiscent or indehiscent legume. It includes about 56 genera of which 6 are represented in Saudi Arabia as natives or introductions.