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.
The Selaginellaceae includes only one genus, Selaginella.