What is the white plume Cyrano takes with him into death?

de Guiche's white plume marked him as an officer in battle. He threw it away in a battle with the Spaniards, and Cyrano offers to wear it in his stead, noting that a courageous man would never have removed it. Upon his death, the unstained white plume is all that Cyrano has left...... a symbol of his honor and courage.