The yellowish, powdery spores of clubmosses contain flammable pollen that was used as flash powder for the first photographic cameras and by theater pyrotechnists. Clubmosses resemble miniature evergreen trees, having upright stems and horizontal branches that contain spore-bearing cones. For hundreds of millions of years, clubmosses survived many climatic and environmental changes. More closely related to ferns than mosses, these plants grew to gigantic proportions and dominated the earth during the Paleozoic era. The decayed matter of these ancient plants comprises a major portion of coal beds worldwide. Although found in temperate areas, these evergreens continue to chiefly thrive in tropical and subtropical regions.