The Papilionaceae Family, also widely recognized as the legume or Fabaceae family, represents a large and globally distributed plant group. Flourishing across both temperate and tropical zones, this family shares a characteristic fruit type – the pod – with Caesalpiniaceae and Mimosaceae. However, Papilionaceae pods are typically less woody compared to Caesalpiniaceae and less frequently clustered than in Mimosaceae. In regions like West Africa, while tree species within this family are not abundant, climbers, shrubs, undershrubs, and herbs are commonly observed.
Numerous Papilionaceae species have been introduced globally, primarily for food and fodder purposes, highlighting their economic importance. Beyond their practical uses, the family also boasts ornamental species, notably American and Asiatic varieties within the Erythrina, Clitoria, and Pueraria genera. Gliricidia sepium, originating from the West Indies and known as Madre, is a popular example, valued as a hedge plant and for providing yam sticks.
Identifying members of the Papilionaceae family often relies on their distinctive leaves. These are alternate, stipulate, and compound, frequently exhibiting glandular features and possessing both pulvini and pulvinules. Leaflets are conduplicate, and stipels are present in approximately two-thirds of genera, though these can be deciduous, necessitating examination of immature leaves for accurate identification. Exceptions exist, such as Stylosanthes erecta, a common seashore shrub, which lacks stipels, as do certain genera with paripinnate leaves.
The flowers of Papilionaceae species are characteristically ‘papilionaceous’ and distinctly zygomorphic. This means they exhibit bilateral symmetry and a unique petal arrangement where the adaxial petal (the vexillum or standard) is positioned outside its neighboring petals (wings and keel). Regarding the stamens, nine out of the ten are typically fused into an abaxial trough, while the tenth, adaxial (vexillary) stamen, situated opposite the standard, remains free.
While compound imparipinnate or digitately trifoliolate leaves are prevalent within the family, the occurrence of unifoliolate, compound paripinnate, and digitate leaves, though less common, is distributed across a wide range of genera. This diversity in leaf morphology renders leaf type alone insufficient for definitive identification within the Papilionaceae family, emphasizing the need to consider a combination of characteristics for accurate classification.
