Legumes

The second most important plant family in the human diet (after grasses), legumes owe their protein power to a symbiosis: soil bacteria (Rhizobium) colonize the roots and convert atmospheric nitrogen into plant-usable form, allowing legumes to accumulate 2–3× the protein of wheat or rice. Four legumes were so prominent in ancient Rome that they gave names to distinguished families — Fabius (fava), Lentulus (lentil), Piso (pea), and the most celebrated, Cicero (chickpea).