rye was once the main cereal in northern europe. it tolerates the cooler dryer climate and for centuries, while the more affluent enjoyed white bread made with imported wheat. the poor continued to eat bread made with the grain that was cheap and readily available. when wheat become relatively inexpensive in germany, white wheat flour was used by all the very poorest, either by itself or with rye flour. there is consequently a great variety of german breads. some are baked in pans. but the majority are baked on the bottom of the oven and are evenly crusty.