Evolution allows organisms to evolve with more beneficial traits that prepare the organisms to survive better in their environment. Sometimes plants will have modified stems that gradually alter themselves in order to give the plant a better chance of survival. This picture is of a potato. Potatoes are tubers that are modified stems of potato plants. Tubers contain the normal aspects of regular stems, such as nodes and internodes. The nodes are the eyes of the potato. The tubers are storage organs for the potato plants that store nutrients for the plant, which help it during the winter months.