Ecological-genetic differentiation and dry storage temperatures regulate the germination of caryopses of Hordeum spontaneum, the wild type of cultivated barley. Freshly harvested caryopses of H. spontaneum in their spikelets (dispersal units) did not germinate, but separated embryos did. After dry storage for more than 68 days at high temperatures, caryopses in their dispersal units germinated. The degree of after-ripening (dormancy) was found to differ in the 3 local populations tested in this study. The highest germination occurred in caryopses collected from the northern-facing slope of Nahal Oren, Mount Carmel, the most humid habitat tested. An intermediate result was from the opposite southern-facing slope, and the lowest germination was observed in those from the Negev Desert near Sede Boker. The germination level of caryopses from spikelets stored dry at low temperatures such as –18 °C remained poor for a long time. The ecological significance of this study is discussed.