A clarification of the generic limits of Trigonella and Medicago

Abstract

The main steps in the history of delimitation of Medicago and Trigonella are given. The typical medicagos have been characterized by spirally coiled pods; the typical trigonellas, by cylindrical straight or curved pods. The cause of the long disagreement is due to the existence of species having flattened or compressed pods in both genera. Such species were considered by most botanists to be intermediate between Trigonella and Medicago. Some botanists included all these species in Medicago whereas others included them in Trigonella. Some proposed an intermediate genus, e.g. Pocockia, Melissitus. In 1873, Urban suggested the characters of the cotyledons as the only reliable criteria for delimitation between the two genera. New evidence based on floral characters supports Urban's generic concept. A possible parallel evolution of pod shape is assumed to have occurred in both genera.