This document summarizes key characteristics of the Fabaceae family (Leguminosae), including that it contains over 18,000 species of herbs, shrubs, trees and vines. It notes that leaves are usually compound but sometimes simple, and flowers are typically bisexual with 5 sepals and 5 petals. The stamens number 5 or more, and the gynoecium has a single carpel. The fruit is generally a legume. It provides examples of distinctive features of the Caesalpinioideae subfamily, such as zygomorphic flowers with 5 distinct stamens and petals.

1. Fabaceae Caesalpinioideae

2. Fabaceae(Leguminosae) — Bean/Pea family (after faba, Latin name for broad bean). 643 genera / 18,000 species.

3. The Fabaceae consist of herbs, shrubs, trees, or vines, with spines sometimes present The leaves are usually compound (pinnate, bipinnate, trifoliolate, rarely palmate), sometimes simple or unifoliolate, usually spiral, basal pulvini often present, sometimes functioning in tactile ( thigmonastic ), leaflet folding responses (e.g., Mimosaspp.), generally stipulate, sometimes stipellate, stipules spinose in some. The inflorescence is variable, typically bracteate. The flowers are usually bisexual, sometimes unisexual, actinomorphicor zygomorphic, pedicellate or sessile, hypogynous or perigynous. The perianth is biseriate, dichlamydeous, with a hypanthium sometimes present.

4. The calyx is aposepalousor synsepalous with 5 [3 6] sepals. The corolla is apopetalous or sympetalous, with 5 [rarely 0] valvate or imbricate petals. The stamens are 5 or 10 ∞, distinct or connate. Anthers are longitudinal, rarely poricidalin dehiscence. The gynoecium is unicarpellous, with a superior ovary, 1 [rarely 2 or more in some Mimosoideae] carpel, and 1 locule. The style and stigma are solitary. Placentationis marginal; ovules are anatropous or campylotropous, bitegmic, 2 ∞ [1] per carpel. Nectaries are often present as a ring at the base of the ovary. The fruit is generally a legume, sometimes indehiscent (e.g., Arachis, peanut), winged (a samara), drupelike, or divided into transverse partitions (a loment).

5. The Caesalpinioideae are distinctive in having generally zygomorphicflowers with usually 5 or 10 [1 ∞] distinct stamens (staminodes present in some) and a corolla (imbricate in bud) with typically five distinct petals (sometime reduced or lacking), the posterior, median petal inner to (overlapped by) the two lateral petals.

6. A.Amorphafruticosa, Whole plant. B. Amorphafruticosa, Close-up of owers of spike.

7. C. Bauhinia variegata. Note medial posterior petal inner to laterals and distinct stamens. D. Caesalpiniaspinosa. Note unusual pectinate anterior sepal.

8. E. Cassia didymobotrya, with heteromorphic (trimorphic) stamens. . F. Sennaarmata, a desert species

9. Reference/s: Plant Systematics by Michael G. Simpson

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