: Plants with creeping and erect stems; roots poorly developed. Leaves numerous, simple, 1-veined, with a ligule (membranous flap) on the upper (adaxial) surface, either all leaves simlar and spirally arranged or of 2 kinds and 4-ranked. Sporangia located on the adaxial surface of a sporophyll, these groups in terminal strobili; spores differentiated into megaspores and microspores; megasporophylls located at the base of the strobili, microsporophylls in the upper portion. Spores tetrahedral.
Selaginella, the only genus in the Selaginellaceae, includes about 750 species, most of which are tropical in their distribution.