Treatment of the genera of beans varies among flowering plant classification systems. As indicated by a browse of the Flowering Plant Gateway (placed by Thorne in the Superorder Rutanae and Takhtajan in the Subclass Rosidae) these plants are often placed within a single unit at the family level, the Fabaceae (Leguminosae) with clusters of related genera placed, as was the case with Cronquist's treatment of the Rosaceae, in a group of (usually - although see Thorne' treatment) three subfamilies. Cronquist prefers to treat this group of three at the family level, with all linked at the rank of Order. Since definition of these three lineages rests on a suite of conspicuous characters and the only differences among various treatments is a simple matter of rank, we will follow Cronquist's treatment. Elements of Fabales include about 730 genera and over 19,000 species distributed across the planet; the Texas Flora include 81 genera, 398 species, and 138 infraspecific taxa.
In direct contrast to the Rosaceae, the unifying feature of this group is the gynoecium and key characters that allow one to distinguish between families of the Fabales (or subfamilies of the Fabaceae s. lat.) are associated with the androperianth.
All taxa are linked via a monocarpic gynoecium or simple pistil that is usually (rarely reduced to an achene) multi-seeded with dehiscence along two sutures in most cases, sometimes indehiscent, and - in the case of the loment, the fruit breaks into single-seeded sections:
Key to the Families of the Fabales:
1. Flowers actinomorphic (perianth connation sometimes present)
More information on the Fabales: Fabaceae, Leguminosae, Caesalpiniaceae, and Mimosaceae