Coloured scanning electron micrograph (SEM) of spores from a stiff clubmoss (Lycopodium annotinum). Spores are the asexual reproductive cells of a clubmoss plant. The stiff clubmoss is found on mountains and in northern areas of North America, Europe and Asia. Lycopod mosses were widespread during the Carboniferous period (345-280 million years ago). Magnification: x1,700 when printed at 15cm wide.