European and Asian plants assignable toMedicago rigidula(L.) All., as this species is currently interpreted, were found to differ morphologically. Indeed, a combination of morphological, geographical, and interbreeding evidence supports the recognition of the European and Asian plants presently interpreted asM.rigidulaas separate species. The best characters for distinguishing plants of the two continents are number of pollen pores (pollen consistently 3-pored in European plants, and consistently 4-pored in Asian plants), number of coils in the pod (averaging 4.5 in European plants, 5.5 in Asian), and fruit spine morphology (usually more hooked and longer in European compared to Asian plants). Plants of North Africa require further study, but the specimens examined were generally closer to European than to Asian plants. The chromosome number of 28 Asian collections, 24 European collections, and 3 African collections was constant, withnensp;=ensp;7.
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