19 Reading 3-1 On the list of 30 major food crops, the Mediterranean region contributed: wheat, barley, pea, rapeseed, and the wild races of oats and rye. The annual production is on the order of 730 million metric tons. The savanna formation includes both open grasslands with widely scattered trees and dry forest where the dry season lasts some 5-8 mo each year. The regime favors both seedy annuals and plants with tubers that behave like annuals. Tuber formation is an adaptation to long dry seasons. At the onset of the rains, the tubers of yams, for example, sprout and the vines grow with remarkable vigor; virtually the entire contents of the tuber are mobilized and trans-located upward. At the end of the rains, the process is reversed and nearly all of the food stored in the vine is trans-located downward and the tuber grows very rapidly. The vine dies and the tuber remains dormant through the dry season and safe from f res that often burn the vegetation at that time. The annual habit is also suited to long dry seasons. Seeds can survive the drought and sprout at the onset
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