 Complete the following phrase:  Ambrosius Volmar Keller is Baldungs largest and last portrait painting, and the only one in which he used a landscape as a background. The symbolism of the conspicuous grapevine growing behind Kellers back has not been entirely explained, it could be related to Christianity or to Northern European Renaissance humanism. The fact that Keller is sitting on the left and looking to the right suggests that the portrait may have had a lost pendant, maybe a portrait of the elder Keller. The donation of the painting to the Strasbourg museum by Emperor Wilhelm II constituted an important gesture in the early stages of the reconstruction of the municipal collections, which had been totally destroyed in 1870, during the 