Tree trunks and branches are ornamented with many species of ferns, "Lycopodium", lichens, and orchids. The genus "Lycopodium" was first published by Carl Linnaeus in 1753. Some sources do not recognize the genus, sinking it into "Lycopodium". It is treated as section "Obscura" when retained within "Lycopodium". Several species have been used economically for their spores, which are harvested as Lycopodium powder. The spores of "Lycopodium" species are harvested and are sold as lycopodium powder. In this approach, "Lycopodium" sensu lato has about 40 species. "Lycopodium clavatum" has a widespread distribution across several continents. The species was first described by Carl Linnaeus in 1753 as "Lycopodium apodum". For many years, this species was known as "Lycopodium flabelliforme" or "Lycopodium digitatum". Lycopodium powder is a yellow-tan dust-like powder historically used as a flash powder. Other plants with similar reproductive means include the "Psilotum", "Lycopodium", "Selaginella" and "Equisetum". As a then-common laboratory supply, lycopodium powder was often used by inventors developing experimental prototypes. Other plants with similar life cycles include "Psilotum", "Lycopodium", "Selaginella" and "Equisetum".