The Class Lycopsida includes the clubmosses. These plants are often loosely grouped as the fern allies. The Lycopsida traditionally included all the clubmosses, including Selaginella and Isoetes. However, subdivisions within the Division Lycophyta are now considered ancient enough to warrant higher-level separation in accordance with cladistics.
The clubmosses are thought to be structurally similar to the earliest vascular plants, with small, scale-like leaves, homosporous spore borne in sporangia at the bases of the leaves, branching stems (usually dichotomous), and generally simple form.
The Class Lycopsida contains a single living order: the Lycopodiales. There are two major groups of large clubmosses: the Lycopodiaceae and the Huperziaceae. The Family Lycopodiaceae comprises the extant genus, Lycopodium, which includes the Wolf's-foot clubmoss, Lycopodium clavatum, Ground-pine, Lycopodium obscurum, Southern ground-cedar, Lycopodium digitatum, and other species. Also included are species of Lycopodiella, such as the Bog clubmoss, Lycopodiella inundata. Most of the Lycopodium favor acidic, sandy, upland sites, whereas most of the Lycopodiella favor acidic, boggy sites.
Lycopodiella cernua, a creeping clubmoss with erect growth
(shown here) occurring at intervals
The other major group, the Family Huperziaceae, are known as the firmosses. This group includes the genus Huperzia, such as the Shining firmoss, Huperzia lucidula, the Rock firmoss, Huperzia porophila, and the Northern firmoss, Huperzia selago. This group also includes the odd, tuberous Australian plant Phylloglossum which was, until recently, thought to be only remotely related to the clubmosses. However, recent genetic testing has shown it to be very closely related to the genus Huperzia.
Dried spores of the common club moss, known somewhat inaccurately as lycopodium, were used in Victorian theater to produce flame-effects. A blown cloud of spores burned rapidly and brightly, but with little heat. It was considered safe by the standards of the time. The effectiveness of the spores in this respect may possibly be due to their high uptake of aluminum from the soil.