The subclass Lycopodiidae consists of one family, the Lycopodiaceae, containing 2-5 genera and 450 species. The most familiar genus is Lycopodium, also known as clubmoss or ground pine. These are terrestrial, perennial, evergreen plants, which grow rooted in the soil or forest floor, and have creeping or erect stems and numerous small, scale-like leaves. Their haploid spores are produced in a club-like structure known as a strobilus. Species of Lycopodium are found on all continents (except Antarctica) and many oceanic islands. Some species familiar to North America are the ground pine (Lycopodium obscurum), ground cedar (L. complanatum), and running clubmoss (L. clavatum). No substantial economic products are obtained from species of Lycopodium. The spores are rich in a volatile oil, and have been used to make explosive powders. Rhizomatous strings of some species are sometimes collected and used to make evergreen Christmas wreaths.