Similar to ferns, clubmosses exhibit alternate generations, oscillating between an underground sexual phase of the plant and an above ground spore-producing version. The yellowish, powdery spores of the clubmosses have been gathered for human use for many years. They contain a flammable type of pollen that was utilized as flash powder for early photographic cameras and was frequently an ingredient of fireworks. The spores also have a long history of use in medicinal treatments, especially in dusting powders formulated to remedy conditions such as eczema, intertrigo, herpes, and ulcers.